Table 2.

Data extraction: Qualitative studies.

Author(s)	Title	Outlet (journal, dissertation, report)	Year	Type of special education setting (e.g., resource class, special school)	Class size information	Study location	Study design
Gottlieb (1997)	An evaluation Study of the Impact of Modifying Instructional Group Sizes in Resource Rooms and Related Service Groups in New York City	Report	1997	Resource rooms and speech services	In elementary school: 16,26 in 1994‐1995, and 24,39 in 1995‐1996.	New York City, U.S.	Evaluation design using questionnaires, interviews observations, and achievement data.
					In middle school: 20,02 in 1994–1995, and 30,21 in 1995–1996.
					No accurate data for high schools.
Huang (2020)	Special education teachers’ perceptions of and practices in individualising instruction for students with intellectual and developmental disabilities in China	Dissertation	2020	Special education schools	Class size ranged from five to 14 students (M = 9,4).	Shanghai, China	Interview study
Keith (1993a)	Special Education Program Standards Study. Commonwealth of Virginia. Final Technical Report	Report	1993	Special education classes	Not specified	Virginia, U.S.	Mixed‐methods evaluation study using interviews, observations, document review, and a survey
Prunty (2012)	Voices of students with special educational needs (SEN): views on schooling	British Journal of Learning Support	2012	Special schools or special education classes in mainstream schools	Not specified	Ireland and England	Interview study (focus groups, and individual interviews)
MAGI Educational Services, Inc. (1995)	Results of a Statewide Research Study on the Effects of Class Size in Special Education	Class Size Research Bulletin	1995	Modified Instructional Services (MIS) I classes which covered classes for students who required instructional services in a special class with opportunities for mainstreaming. Students could supposedly spend both full‐time or less in these classes, depending on pull‐out services or involvement with mainstream classrooms.	Class size was increased from 12 to 15 students.	New York, U.S.	The study consisted of a descriptive part and an experimental/observational part. Focus here is on the descriptive study which used a number of complementary data collection methods including document review, public hearings, focus groups, surveys of key informants, and record review.

Author(s)	Theoretical perspective	Research objectives	Student age and gender	Characteristics of student group (e.g., category of special needs, SES)	Teacher education and experience	Parent characteristics (e.g., SES)	Overall quality appraisal
Gottlieb (1997)	Not specified	To evaluate the impact of increased group size on the quality and availability of resource rooms and related service instruction.	Not specified	Not specified	Participants were resource room teachers (representing all levels of schooling), speech therapists, and general education teachers (who had resource room students enroled in their classes).	Not specified	Include for analysis. No philosophical or theoretical perspectives presented and not a lot of information on methods and analytical procedures. However, the paper works well as an evaluation report, and the design chosen is appropriate for an evaluation. The conclusions drawn flow from the descriptive data presented.
Huang (2020)	Critical realism	To investigate and describe Chinese special education teachers’ perceptions and practices related to individualising or adapting instruction for students with intellectual and developmental disabilities.	Grades 1–6	Students with intellectual and developmental disabilities, covering both autism, physical impairments, and intellectual disabilities. Other types of disabilities were less frequently represented.	The participating teachers were Chinese language arts and math special education teachers with an average of 14,6 years of experience teaching students with intellectual and developmental disabilities (range was three‐26 years). All but two participants held Bachelor's degrees as their highest educational level.	Not specified	Include for analysis. Class size is not the main topic of the study, but it is touched upon. The study is well‐performed and clearly reported.
Keith (1993a)	Not specified	To investigate Virginia special education program standards, focusing on local applications of the standards for class size and class mix and the effects of varying class sizes and mix on student outcomes.	Students were from preschool, elementary, middle, and high school. Boys made up 70% of the students in the special education programmes	Students with educable mental retardation, severe emotional disturbance, and specific learning disabilities.	Teachers had worked an average of 6,5 years in their current job, and had worked an an average of 11 years in the field of special education. Almost half the teachers had a Bachelor's degree as their highest educational level, while another 49% held Master's degrees.	Not specified	Exclude from analysis. No philosophical or theoretical perspective stated, very limited description of data collection, and the approach to qualitative analysis is not described. It is unclear in what way the site visits and interview material was used. The paper functions well enough as an evaluation report, but as a qualitative research study, it is inadequately reported and therefore not suited for inclusion.
Prunty (2012)	Perspective of the child	To explore the views of children and young people on their schooling	Not specified	Not clearly presented, but some had physical disabilities, while others had mental disabilities	Not specified	Not specified	Include for analysis. This study is not about differences between different special education settings, but more about differences between mainstream/inclusion and special education. Nonetheless, there are points made here that carry relevance to the issue of special education class size. In terms of methodological quality, the study is well performed and transparently reported.
MAGI Educational Services, Inc. (1995)	Not specified	To examine class size effects on students, service providers, parents, and school districts.	Students were from elementary and secondary grades.	The majority of students were classified as learning disabled.	Not specified	Not specified	Exclude from analysis. No philosophical or theoretical perspective stated, very limited description of data collection, and the approach to qualitative analysis is not described.