Research Trend in the Practice of Differentiated Instruction

The influence of diversity in education has affected the shift in pedagogical practice, moving from the traditional teacher-centered classroom to student-based teaching approach. Such teaching approach that has received extensive review from educators as well as researchers is differentiated instruction. Differentiated instruction has been practiced in numerous contexts with different types of students around the globe, in various academic subjects such as languages, mathematics, and sciences. Simultaneously, researchers, and practitioners alike, have indicated growing interest in conducting studies in the practice of differentiated instruction. These studies contributed to the expansion of the use of differentiated instruction in teaching and learning as well as in the improvement of its practice and students‟ learning outcomes. This paper therefore discusses the current trend, or perspectives, of the researches in the practice of differentiated instruction, highlighting the research contexts, objectives, methods, and findings.


Introduction
The influence of diversity in education has affected the shift in pedagogical practice, moving from the traditional teacher-centered classroom to student-based teaching approach. Such teaching approach that has received extensive review from educators as well as researchers is differentiated instruction. Differentiated instruction has been practiced in numerous contexts with different types of students around the globe, in various academic subjects such as languages, mathematics, and sciences. Simultaneously, researchers, and practitioners alike, have indicated growing interest in conducting studies in the practice of differentiated instruction. These studies contributed to the expansion of the use of differentiated instruction in teaching and learning as well as in the improvement of its practice and students" learning outcomes.
Extensive review of literature has been conducted to explore the essence of the researches exploring the practice of differentiated instruction. The existing studies consist of an accumulation of various themes in the implementation of differentiated instruction in academic subject areas such as languages, mathematics, and sciences. In one area, differentiation studies have looked into various groups of learners that include mixed-ability students, high-ability students, and also students with learning disabilities (Baumgartner et al., 2003;Lawrence-Brown, 2004;Rock et al., 2008;Tieso, 2001a); (Geisler et al., 2009). In another area, researchers have investigated the varying influence of differentiated instruction on the learning outcomes of students such as motivation, engagement, attitude, emotion or desire to learn (Cheng, 2006), (Brimfield et al., 2002;Skinner and Belmont, 1993;Tieso, 2001b) (Heacox, 2009;Logan, 2011;Olah, 2008). Another scope of differentiation studies that is related to either English language or language arts learners highlights the common or best practices and effects on student achievement (Aliakbari and Khales, 2014;Hung, 2015;Karadag and Yasar, 2010;Langley, 2015;Renkema, 2014), (Gorman, 2011;Wallis, 2015). Moreover, this review also revealed related studies benefitting gifted education, revealing its best practices, and effects on achievement and motivation of gifted learners, in various academic subjects (Ann and Sizemore, 2015;Brulles et al., 2010;Caldwell, 2012;Launder, 2011;Martin and Pickett, 2013;Powers, 2008;Reis and Boeve, 2009;Ruggiero, 2012;White, 2013), (Altintas and Özdemir, 2015;Brulles and Winebrenner, 2012;Edwards, 2007;Hyde, 2007). The following sections discuss the current trend, or perspectives, of the studies conducted in investigating the practice of differentiated instruction, highlighting the research contexts, objectives, methods, and findings.
Despite the limited number of research contribution in the international context, there were few studies of differentiated instruction conducted in the South East Asia region such as Malaysia (Jin, 2015;Meyad et al., 2014) (Yamat et al., 2011). Those studies were conducted in Sg. Petani, Kedah;Bangi, Selangor;and, Serdang, Selangor. Jin (2015) conducted a mixed methods study investigating the practice of differentiated instruction in one school in Sg. Petani, Kedah focusing on reading. The study investigated a) the relationship between differentiated instruction and student readiness, interest, and learning profiles, and b) teachers" views on differentiated instruction on 2 English teachers and 76 Form 3 students. The study found that differentiated instruction is time consuming although it greatly improved students" interest to learn English. Meyad et al. (2014) conducted an experimental study investigating the effect of differentiated instruction on student motivation in one school in Serdang, Selangor focusing on Arabic language. The study investigated students" motivation having experienced differentiated instruction gathered through instrumental and MSLQ questionnaires. The data were collected from 100 Form 4 students. The study found that the students from the experimental group were generally more motivated than the control group, which proved that the differentiated instruction is an effective approach in improving students" motivation towards studying the Arabic Language as a foreign language. Yamat et al. (2011) conducted a qualitative case study exploring the implementation of differentiated instruction in an enrichment writing course for gifted children called "Crafting the Essay", during a School Holiday Camp program in Bangi, Selangor, focusing on writing. 15 gifted students participated in the program and contributed to the data collected through observations and interviews. The study revealed that teachers need to encourage students. This would help students develop confidence as they enjoyed the lesson, and were more creative and descriptive in their thinking. In addition, grouping contributes to improvement as students had the opportunity to work on each other"s work. Despite such positive learning outcomes, teacher revealed that differentiated instruction is meaningless or useless. It requires much effort, organization, preparation, and commitment.
The existing contexts of research where the investigation on the practice of differentiated instruction were conducted revealed that its practice is not as widespread/ rampant as it appears to be. Most of the studies, however, came from the U.S. where its practice is policy-bound, making it compulsory for teachers to differentiate their lessons, and thus making convenient for researchers to find their research contexts. Thus, this explains the greater contribution of studies from the U.S.
Conducting a research (pertaining to the practice of differentiated instruction) in contexts other than the U.S. may require extra effort, or intervention, by researchers e.g. to train the teacher participants about differentiated instruction before the actual research can begin. This may stretch the research span to be longer, and incur extra financial research cost. This factor explains the inadequacy of researches on differentiated instruction, especially in the South East Asia region as shown in Table 1 above.

Subject Areas
The current researches on differentiated instruction reviewed indicate that the studies had been conducted on numerous subject areas. In Table 2 below, the subject areas were categorized into a) languages, b) mathematics, c) sciences, d) others, and e) combination of 2 or more subjects.
The existing researches on differentiated instruction mentioned above seem to indicate that most of the studies came from the languages subject area, but that is not the case. The languages category comprise of various types of English language courses i.e. ESL, EFL and ELA; language skills, i.e. reading, writing, listening, vocabulary; and other world languages i.e. Arabic, Turkish, and Spanish. It can be seen that most of the studies were contributed from the mathematics subject area. This serves to rationalize that more studies investigating the practice of differentiated instruction focusing on English language teaching and learning are needed. Next, the following section will discuss the scope of the research objectives and approaches adopted by the previous studies in investigating the practice of differentiated instruction.

Research Approaches and Objectives
As shown in Table 3 below, most of the recent studies investigating differentiated instruction employed either quantitative or qualitative approach. Several studies had employed explanatory mixed methods, while few had attempted exploratory or concurrent mixed methods. The rationale to employ a particular approach depends on the research objectives.
Quite a number of studies had employed mixed methods, although most of them were explanatory i.e. quantitative method precedes qualitative method. Studies employing explanatory mixed methods had examined the effect of differentiated instruction on students" achievement, examined students" motivation, engagement, or attitude, and investigated teachers" practices (Behncke, 2015;Jin, 2015;McCarty et al., 2016;Wan, 2015); (Hung, 2015); (Sizemore, 2015); (Amadio, 2014;Joseph et al., 2013;Karadag and Yasar, 2010); (Flaherty, 2010) (Palmer and Maag, 2010a); (Koeze, 2007); (Hyde, 2007). Only three studies were found to have employed exploratory mixed methods (Swaby, 2016); (Hubbard, 2009;Santisteban, 2014) while only one attempted concurrent mixed methods (Chamberlin and Powers, 2010). In the exploratory mixed methods, qualitative method precedes quantitative method. The existing studies utilizing exploratory mixed methods had explored the impact, or effect, or relationship, of or between differentiated instruction and student achievement, student attitude, student perceptions, and also investigated teachers" practices. Through concurrent mixed methods, both quantitative and qualitative methods are conducted simultaneously. Chamberlin and Powers (2010) investigated the impact of differentiated instruction on student achievement utilizing concurrent mixed methods.

Finding of the Existing Researches
The existing studies investigating differentiated instruction had revealed several themes of findings. The studies conducted with different contexts, participants, research approaches and objectives yielded varied results and findings. Depending on the research objectives, the themes of the findings include teachers" practices and perceptions towards differentiated instruction, and the impact of differentiated instruction on students" learning outcomes such as achievement, motivation, engagement, attitude, and perception. Table 4 displays the summary of findings related to teachers" practice. The existing studies that explored teachers" practice of differentiated instruction revealed varied findings that can be categorized into several themes.

Findings Related to Teachers' Practice
Some studies had highlighted the importance of assessment of students ability levels (Burris, 2011;McQuarrie and McRae, 2010;Olah, 2008;Servilio, 2009); (Gentry et al., 2013). (McQuarrie and McRae, 2010) for example, stated that differentiated instruction not only begins with, but also is determined by ongoing assessments. Burris (2011) also revealed that in providing differentiated lessons that are meaningful, teachers need to assess students" knowledge by using assessments.
There are also studies that highlighted differentiated instruction as a challenging teaching approach (Langley, 2015); (Sizemore, 2015); (Tramonto, 2013); (Burris, 2011;Yamat et al., 2011). In a study investigating best practices of differentiated instruction, (Tramonto, 2013) revealed that differentiated instruction is challenging. It was revealed that although the teacher participants in the study believed that differentiated instruction would benefit students, however, they also believed that implementing differentiated instruction is not feasible. This is perhaps, as revealed by Yamat et al. (2011) in a study, because differentiated instruction requires a lot of effort as well as commitment.
Quite a number of studies have revealed the impacts on students (Sizemore, 2015); (Least, 2014;Yamat et al., 2011); (Jin, 2015); (Olah, 2008); (Least, 2014); (Olah, 2008) Earlier, Olah (2008) stated that differentiated instruction may increase academic achievement. Recently, (Least, 2014) for example found that differentiated instruction was highly effective. It was found that students" scores were higher. In addition, Jin (2015) revealed that differentiated instruction greatly improved students" interest to learn English. Finally, Least, 2014 andOlah (2008) also found that differentiated instruction may increase student engagement by providing activities that suit their readiness or interest. for differentiating instruction that lead to increase student achievement Challenges: teachers indicate that they believe differentiated or responsive teaching would benefit students, they also indicate they do not believe it is feasible for them to differentiate instruction.

Practices:
Reading instruction was differentiated by the use of flexible groups, texts on different reading levels, student-selected texts during independent reading, and guided reading groups according to the identified need for individual students; the need to provide learners with choices about what they read and in the design of their work products so that they are a better match for learners (Yamat et al., 2011) Language, writing An enrichment course "Crafting the Essay"

Bangi, Malaysia
To explore the implementation of DI in teaching gifted children 15 gifted students Qualitative, case study

Interviews, observations
Students developed confidence as they enjoyed the lesson; Teachers encouraged students; Grouping contributes to improvement as students had the opportunity to work on each other"s work; Students were more creative and descriptive in their thinking; Teachers find DI meaningless or useless; DI requires much effort, organization, preparation, and commitment; (Burris, 2011)

Mathematics, Reading
To explore teachers" practice of DI Field log, student survey, student interview, document analysis of student work, Differentiating instruction according to student profile may increase academic achievement; Assessing student readiness is clearly crucial when designing meaningful instruction; support may increase student interest in a topic, and, in turn, student engagement. Table 5 displays the summary of findings related to teachers" perceptions. These include the views, beliefs, perspectives, or attitude expressed by the participants in the existing studies. The findings related to teachers" perceptions also highlighted similar themes as discussed in the previous sections i.e. challenging, time, assessment of students, teaching behaviors, and attitude.

Findings Related to Teacher Perceptions
In a study exploring teachers" perceptions of differentiated instruction by Sabb-Cordes (2016), it was reported that teachers faced challenges in using the strategies. Maddox (2015) stated that differentiated instruction was challenging because teachers found materials were lacking and the need to provide for diverse learner needs. Rodriguez (2012) highlighted that because of the immense amount of preparation time involved coupled with lack of resources, many teachers do not differentiate instruction in their classrooms. Robinson et al. (2014) reported that teachers require a lot of time to differentiate. Amadio (2014) echoed similar point that teachers might differentiate better with sufficient time. Hung (2015) indicated in a study that learner needs are the key for differentiation. Teachers need to constantly assess students and adjust their instruction according to students" current achievement. Likewise, Robinson et al. (2014) reported that teachers differentiate based on student assessments. This is because every student is different and their success depends on the varied strategies used.
In the same study, Hung (2015) also revealed that teachers responded positively on their experience of differentiated instruction. It was reported that providing choice is the key for successful practice of differentiation.
Some other studies had found the effect of differentiated instruction on the attitudes. Wan (2015) revealed that teachers had positive attitudes towards differentiated instruction. However, because of insufficient class management skills and personal teaching beliefs, the implementation of differentiated instruction was in conflict. Hung (2015) also found that differentiated instruction improved student attitude towards learning as they were engaged in group work activities. Teacher and students reported positively on DI experience; students were generally satisfied with the roleplay activity and being offered choices of tasks; students enjoyed the activities; providing a choice of tasks are the keys of a successful DI classroom; The need of each student is key for planning; Content and assessment is multi-leveled; DI improved students" learning attitudes as students engaged in activities and group work; The teacher constantly adjust their instruction based on students" performances in the assessment. (Maddox, 2015 Table 6 displays the summary of findings related to the impact of differentiated instruction on student achievement. The findings related to student achievement can be found in most of any studies investigating the practice of differentiated instruction. The findings however differ or vary depending on the research objectives. Some studies had found positive effect on student achievement while others negative.

Findings Related to Student Achievement
Some studies had found significant increase in student achievement. According to Azah (2016), there was a significant improvement in the student performance of decoding and fluency skills i.e. in reading. Likewise, Behncke (2015) also generated a significant increase in the fluency scores in the student participants. In a quantitative study involving 374 students, (Muthomi and Mbugua, 2014) investigated the effectiveness of differentiated instruction on student achievement, and concluded that differentiated instruction improved student achievement.
Another pool of studies that examined student achievement had yielded results based on the differences in scores i.e. based on experimental studies involving experimental and control groups. Several studies had found that there was a significant difference between the students in the experimental group (received DI) and the students in the control group (Alavinia and Farhady, 2012;Osuafor and Okigbo, 2013) (Valiande and Tarman, 2011). However, quite a number of studies had generated contradicting results. These studies indicated that there was no significant difference between the achievement of students who received DI and those who did not (Gamble, 2011;Ruggiero, 2012). Additionally, according to Scott (2012), differentiated instruction did not have an impact on overall students" learning.
There were also studies that examined the association between differentiated instruction and student achievement (Corre, 2013;Mulder, 2014;Williams, 2012) Gorman (2011. A study conducted by Gorman (2011) found significant positive association between differentiated instruction and student achievement. However, most of the studies examining the association between differentiated instruction and student achievement post-Gorman (2011) revealed otherwise. Williams (2012) for example, revealed that there was no significant effect between differentiated instruction and students" results. Corre (2013) echoed that student achievement was not correlated to the use of DI. Most recently, Mulder (2014) reported that although differentiated instruction had no significant effect on student achievement, however, it was found in that study that the relationship between differentiated instruction and mathematics achievement was positive. There was a significant increase in the achievement scores of the experimental students, in both gifted and non-gifted groups. (Hung, 2015) Mathematics Netherlands There was a significant difference between students taught with DI and without. (Ruggiero, 2012) English language arts New York State To examine the effects of DI in gifted and talented programs on student achievement 30 4 th grade students, gifted and talented Quantitative Standardized student achievement data There was no significant difference between the achievement of students who did and did not receive DI approach; however, the achievement of students who received DI was slightly higher.

Scott (2012) Mathematics
To determine the effects of DI on student achievement 3 teachers, 75 students Quantitative, quasi experimental Math assessments, pretest, posttest DI did not have an impact on the students" learning in general; Neither male nor female students demonstrated greater achievement at a significant level i.e. DI does not benefit one gender over the other; DI benefits one ability level over the other. (Williams, 2012)  There was no significant difference between the achievement of students taught using DI and traditional instruction; There was no significant difference in the achievement of students from different race and gender; There was no significant difference in student attittude toward maths (of confidence, value, motivation); There were significant differences in student attitude toward maths (of enjoyment) (Brulles et al., 2010)  The treatment group experienced higher growth in performance; providing lesson that "meet student needs will ultimately increase the retention of students" (p. 131). DI based on readiness, interest and learning profile led to enhanced achievement, study habits, social interaction, cooperation, attitude toward school, self-worth, motivation and engagement (Schlag, 2009) Table 7 displays the summary of findings related to the impact of differentiated instruction on students" learning outcomes. The themes of the findings yielded from the review of the existing studies are motivation, engagement, and attitude or interest. These studies reported that differentiated instruction had varied implications on students as reported based on their motivation, engagement, and attitude or interest towards the learning experience.

Findings Related to Impact on Students' Learning Outcomes
Some studies had revealed that differentiated instruction had impacted students motivationally (Berntsen, 2016;Meyad et al., 2014); (Fenner et al., 2010;Flaherty, 2010;Martin and Pickett, 2013); (Hyde, 2007); (Cheng, 2006). (Berntsen, 2016) for example, concluded in a study that providing choice in teaching motivated students towards learning. In an experimental study, (Meyad et al., 2014) reported that the students in the experimental group receiving DI were more motivated than the students in the control group. The study concluded that differentiated instruction is an effective approach in improving student motivation. Martin and Pickett (2013) revealed that the students participants in their study experienced changes in their motivation in learning. A study by Gamble (2011) however reported a slightly different finding. His finding indicated no significant difference in students" confidence, value, and motivation. Other studies reported increase in student motivation (Fenner et al., 2010;Flaherty, 2010); (Hyde, 2007); (Cheng, 2006).
There are also studies that indicated student engagement as one of the impact of differentiated instruction (McCarty et al., 2016;Moreno, 2015); (Martin and Pickett, 2013); (Decovsky, 2012); (Palmer and Maag, 2010a) (Olah, 2008;Santangelo and Tomlinson, 2009) (Hyde, 2007). McCarty et al., (2016) and (Moreno, 2015) reported that differentiated instruction increased student engagement. Martin and Pickett (2013) stated that differentiated instruction positively changed students" perception of their engagement. In relation to this, (Decovsky, 2012) found that students" interest in learning was highly dependent on the activities provided. (Palmer and Maag, 2010a) concluded that differentiated instruction proved to be engaging the students in learning. Santangelo and Tomlinson (2009) mentioned this earlier that "the time, effort, and dedication required for effective differentiation is unequivocally worthwhile when the high level of student engagement and mastery are experienced" (p.320). Olah (2008) and Hyde (2007) also added that differentiated instruction not only increased academic achievement but also student engagement.
Some other studies had documented differentiated instruction affecting attitude. While some studies reported that students had positive attitude toward differentiated instruction (Chien, 2014); (Karadag and Yasar, 2010), and increased students" interest (Olah, 2008); (Cheng, 2006), (Gamble, 2011) however indicated that there was no significant difference in student attitude. The experimental group was generally more motivated than the control group which proves that the DI is an effective approach in improving students" motivation towards studying the Arabic Language as a foreign language. (Martin and Pickett, 2013)

Mathematics
To investigate the effect of DI on student motivation and engagement 25 gifted students Quantitative Student attitude survey DI positively impacted changes in students" perception of their engagement and motivation (Decovsky, 2012)

High school science
To explore the effect of DI on students" interest 11 students, 3 teacher High school, gifted and talented students There was no significant difference between the achievement of students taught using DI and traditional instruction; There was no significant difference in the achievement of students from different race and gender; There was no significant difference in student attittude toward maths (of confidence, value, motivation); There were significant differences in student attitude toward maths (of enjoyment) (Fenner et al., 2010)

ESL, Science, Language Arts
To explore the effects of DI on student motivation 6 th , 7 th , and 8 th graders Mixed methods Self-assessment motivation survey, Motivational behavior checklist, Pre and post motivation questionnaire DI allowed students to be motivated Implementation of DI improved students" learning and increased student motivation. (Flaherty, 2010 (Horwitz et al., 1986) DI increased student motivation and interest; When content, process, product are differentiated according to students' readiness, interest and learning profile, English learning is more interesting and creates higher motivation; DI did not produce significant decrease in anxiety level.

Discussion and Conclusion
The discussion on the current researches of differentiated instruction above has unfolded the perspectives within the realm of the current researches investigating the practice of differentiated instruction. This paper revealed that studies investigating the practice of differentiated instruction have some common features despite differences in terms of the research contexts as well as the research objectives and methods of inquiry. As a whole, this review concludes that differentiated instruction, despite continues to be challenging for teachers, is deemed pertinent as a pedagogy that it encompasses the elements that are required of teachers to apply in their preparation for a differentiated lesson; that it benefits and applicable not only to a particular group or type of learners as well as academic subject areas. Thus, continuous researches should be undertaken to explore differentiated instruction in order to benefit both the teachers and students.
To sum up, much of the research contribution came from the international contexts, with most of the studies came from the American continent while very few studies came from other parts of the world such as Asia, European, Africa and the Arab countries. Likewise, only few studies were found for the South East Asia region indicating that more researches are definitely needed in this particular part of the world.
These existing studies had focused on several subject areas such as languages, mathematics, and science while some others had explored the practice of differentiated instruction in two or more subjects. Most of the contribution however came from the studies investigating the practice of differentiated instruction in mathematics and reading. More studies are needed in exploring the practice of differentiated instruction in the teaching and learning of English language as well as on other subject areas such as sciences.
Although the existing studies had attempted exploring the practice of differentiated instruction with various research objectives and approaches, few studies had employed exploratory mixed methods, and focused on teachers. Most of the research objectives of these studies varied; ranging from investigating teaching and learning outcomes such as achievement, motivation, engagement, attitude, teachers" perceptions, to teachers" practice. These studies, thus, indicate the "post-pedagogical impact" on students, revealing either positive or negative effects as well as the difficulties posed by the teaching approach i.e. differentiated instruction. This explains the lack of studies focusing on the actual teaching scenario in the classroom i.e. the how-to that documenting the actual differentiation strategies employed by teachers. Thus, a study that focuses on investigating teachers" practice of differentiated instruction would be very beneficial -not only in explaining its relative impact on students" learning outcomes (as revealed in the existing studies)but also would be able to highlight at which juncture of its implementation is the most appropriate and at which requires improvement.
The inadequacy of such research focusing on teachers" implementation of differentiated instruction may be due to the unavailability of specific or related research instrument to gather data for related studies investigating differentiated instruction. This review found that no specific research instrument was employed, or developed, for a particular research objective exploring the practice of differentiated instruction. For example, most of the studies investigating students" motivation accumulated the data based on teachers" perceptions towards the students. A selfchecked questionnaire would be very useful and convenient to be used in that kind of study. Thus, a specific questionnaire measuring students" motivational perspective towards differentiated teaching would provide greater impact in the field of differentiated instruction and its practice.
On that note, future researches in differentiated instruction should explore the relationship between differentiated instruction as practiced by the teachers, and examine its impact on students" learning outcomes e.g. motivation or achievement, through exploratory mixed methods approach, guided by appropriate educational theories and differentiation model.