The COVID-19 pandemic has posed an unprecedented global challenge to all aspects of our lives, including the field of education. In this time of crisis, schools in many countries were forced to close, and students’ learning was disrupted [1]. Even though traditional in-person classrooms could not take place in schools, the doors to learning and teaching were not really closed.

Amid the global pandemic, teachers across the world needed to adapt quickly in response to the pressing need to continue the delivery of education and keep students engaged in learning [2]. Instead of face-to-face instruction, online distance learning became an alternative way for students to attend school. However, the rapid transition to emergency remote classrooms without proper training left teachers with no time for careful preparation and planning. In addition, to look after the different needs of students despite the pandemic, alternative ways of reaching students and advancing their learning were needed immediately. One of the common challenges was the integration of technology in a remote and hybrid learning environment [3]. Most of the technological pedagogical knowledge of teachers was gained in pre-service education and professional development after graduation [4], and teachers had to upgrade their digital literacy skills so that they could play a primary role in encouraging learners to embrace technological literacy during the pandemic. Furthermore, poor interaction between teachers and students in a remote or hybrid environment can be a challenge for teachers, which further complicates the implementation of differentiated instruction (DI) [5]. Due to the lack of face-to-face contact, extra work is required from teachers to increase students’ motivation to learn during the online learning process [6]. In addition, in order to implement differentiation in remote teaching, teachers have to make even greater efforts to address students’ individual academic and social–emotional needs in the virtual learning environment. However, it can be difficult for teachers to assess individual needs and provide tailored instruction for students remotely [7]. Therefore, teachers are required to constantly reflect on their instruction while integrating differentiation and online assessment methods in their daily teaching during the pandemic [8].

Overall, the COVID-19 pandemic caused a significant shift in education, as teachers with traditional teaching approaches moved into a distance learning space. In response to the need to maintain the continuity of students’ learning, teachers were involved in the exploration of new pedagogical practices to support remote learning. The literature has suggested that, while implementing DI during the pandemic could be challenging, it was nonetheless possible with the use of technological tools and a variety of instructional strategies.

Catering for the growing learner diversity in the same classroom has long been a challenge for many teachers. DI is a teaching approach that involves tailoring instruction to meet the diverse learning needs of individual students. In response to students’ readiness, interests and learning profiles, teachers can implement differentiated teaching by modifying the four curriculum components: content, process, product, and environment [9]. With the aim of maximizing the capacities of each student, DI is a proactive approach that enables students to develop their potential by providing them with appropriate scaffolding, supported by a variety of instructional strategies and materials that address their needs ^[10][11][10,11].

A number of studies investigate teachers’ practices of differentiation in two aspects: which teaching practices and techniques do teachers use and what do they differentiate ^[12][13][12,13]. Teachers may provide students with content that has been modified for them, offer different options for the learning process, use different assessment tools, or modify the learning environment to meet the needs of students [14]. Additionally, teachers may give some students more time for learning or, on the other hand, encourage high achievers to learn more quickly [15]. In terms of the process, teachers could tailor instruction throughout the lesson or pre-teach to meet the needs of the students [16]. To differentiate instruction for the entire class, it is common practice to split the teaching content into manageable blocks or units. The teacher provides all students with the same instructions for each unit [15], and then is informed via a formative assessment of which students have achieved the required level of mastery. Students that fall short of the expected standard are given further instruction or individual practice [15]. However, the learning objectives do not change even though each student’s learning paths are unique. It is notable that formative assessment and DI go hand in hand, as high-quality differentiation is based on ongoing assessment and adaptive strategies to meet students’ needs ^[13][17][18][13,17,18]. Teachers could also use flexible groups, which is a mix of heterogenous and homogenous groupings, to structure their instruction in response to students’ need.

The previous literature has indicated the advantages of implementing DI in educational settings. Studies have shown that DI leads to increased levels of student engagement and learning motivation, as reported by Johnsen [19] and McAdamis [20]. DI can also lead to improvements in students’ problem-solving skills, decision-making abilities, and overall cognitive development ^[10][14][10,14]. Additionally, DI has been found to elevate learner confidence ^[12][21][12,21] and improve overall and subject-specific academic results such as reading fluency and comprehension [22] and mathematics achievement ^[23][24][23,24]. The majority of earlier studies has focused primarily on how DI practices affect students’ academic achievement. The potential impact of DI on students’ socio–emotional outcomes, such as students’ motivation and attitudes in differentiated settings, has received very little attention [15]. The effects of students’ perceived DI on their wellbeing, social inclusion, and academic self-concept were examined in a study by Pozas et al. [25]. The findings showed that these outcomes were positively associated with how students viewed their teachers’ DI practices. However, further research is required to illustrate how DI practices affect students’ socio-emotional outcomes.

Despite the documented benefits, the literature has mixed findings about teachers’ reported usage of DI in their regular classroom. Smit and Humpert [26] discovered that primary and secondary school teachers used DI occasionally, primarily via varying learning objectives and assignments. The uncommon use of DI by secondary school teachers was discovered by Pozas et al. [27], which also noted that teachers at high-track schools tend to use DI strategies less frequently. While Adebayo and Shumba [28] showed the frequent use of a variety of classroom strategies, primary school teachers in Prast et al. [18] study reported a moderate to high range of progress monitoring and instructional adjustments. Although differentiation is thought to offer all students the best learning chances available, teachers remain hesitant to implement differentiation in their classrooms due to the presence of various obstacles [29]. Previous studies have revealed that teachers do not feel capable of delivering DI due to a lack of foundational knowledge regarding the approach ^[30][31][32][30,31,32] or a disconnection between understanding and the actual classroom application [33]. Another common concern involves classroom management ^[34][35][34,35]. Teachers can be hesitant to carry out DI strategies, such as grouping practices, especially in a large class. Many teachers consider that grouping practices pose classroom management challenges, as grouping practices often involve multiple learning activities occurring simultaneously, which leads to increased demands on the teacher’s time and attention ^[9][36][9,36]. In addition, teachers may resist adopting DI due to concerns about increased workload [13], as the planning and implementation can be time-consuming, particularly in terms of lesson preparation and assessment [8].

Although several models have been developed to guide the implementation of differentiation, teachers still find it challenging to put DI into practice, and a clear gap exists between theory and practice [37]. To facilitate the implementation of DI, the research-informed five-dimensional (5D) model of differentiation, which draws on constructivism, the zone of proximal development (ZPD), the theory of multiple intelligences and motivation theory, was designed by Roiha and Polso [9] to provide a more practical, tangible and pervasive framework. The model proposes that differentiation can be approached through the following five dimensions: (1) teaching arrangements, (2) learning environments, (3) teaching methods, (4) support materials, and (5) assessment.

Some of the dimensions of the 5D model correspond to the components of Tomlinson’s [38] model, such as learning environment and teaching methods, but in an expanded way. The model provides five ways of integrating differentiation into teaching, with an emphasis on both macro- and micro-level practices. Macro-level practices are associated with the responsibility of the entire school community, and they are usually planned and designed in advance [39]. By contrast, micro-level practices are related to adaptive teaching, which is more spontaneous and responsive to students’ learning needs ^[9][39][9,39].

Teaching arrangements, which form a macro-level differentiation in the model, refer to the organization of teaching and learning experiences by teachers, such as the grouping of students and co-teaching. Another macro-level consideration, learning environment, refers to where learning takes place, as well as the learning atmosphere. In micro-level teaching, teaching methods refer to the use of varied teaching strategies based on students’ profiles, while support materials are the various learning tools or materials that aim to facilitate students’ learning. Assessment, one of the most essential micro-level components of DI, refers to the methods employed to monitor students’ learning progress and adjust the instruction accordingly [39].

The 5D model of differentiation provides a clear and easy-to-use framework for understanding the essence of DI; therefore, it was used in the current study as a guiding framework for understanding teachers’ experiences of practicing DI during the pandemic.

Due to the increased demands and limited resources during COVID-19, most educators encountered challenges in moving instruction to emergency remote teaching ^[5][40][5,40]. This may have made it more challenging to offer equal learning opportunities for students with diverse learning needs and styles [41]. Few studies have explored the implementation of DI during the COVID-19 pandemic. A study by Satyarini et al. [6] revealed that DI was not fully implemented by teachers during the COVID-19 pandemic, and one of the obstacles faced by teachers may have been a lack of technology proficiency. The immediate need for emergency remote teaching forced teachers to adapt themselves to new technologies and novel modes of teaching and learning, involving content preparation and assessment methods within a medium that may have been previously unknown or unfamiliar to them ^[42][43][42,43]. While there was uncertainty regarding how long the distance learning would last, the abrupt transition from conventional in-person instruction to a blend of hybrid and distance learning produced significant emotional uncertainty and stress among educators ^[7][43][7,43].

Another common challenge faced by teachers in remote teaching was associated with students’ participation in a virtual setting [6]. The learning process during the pandemic, which was conducted in a virtual or blended mode, was different from the learning process usually carried out in offline classroom-centric education. Remote instruction prevented face-to-face interaction in the classroom, students exhibited poor concentration, and teachers found it hard to maintain students’ motivation and engagement in learning, especially if teachers conducted one-size-fits-all teaching for all students [44]. In terms of the implementation of DI, extra work was required to make students focus during lessons, and teachers had to come up with various learning materials catering to students’ diverse needs. However, teachers stated that they lacked time for lesson planning, and group activities in distance learning were therefore very limited [45]. Although online teaching and emergency remote instruction conducted during a crisis are similar in that they both involve delivering instruction through technology, they are distinct in terms of their purposes, planning, and levels of preparation. Online teaching is a deliberate approach that requires careful planning to deliver instruction through a digital platform. By contrast, an emergency remote class is just a temporary shift from face-to-face instruction due to an unexpected crisis or event, with a focus on maintaining continuity of learning and minimizing the disruption to students’ education; thus, students’ diverse needs may not be taken into consideration when designing the teaching content [46].

Many teachers considered online learning to be less effective than learning face-to-face, as learning face-to-face can facilitate socialization between teachers and students, and teachers can observe students’ performance more directly [45]. However, prior research ^[47][48][47,48] demonstrates that information and communications technology (ICT) applications can support student-centred learning and have positive effects on student achievement. More research is required to investigate how ICT can be used in DI as an adaptive tool and not so much as an add-on to conventional teaching ^[47][49][47,49].