Table 4.3.

Characteristics of Studies Used in the Data Synthesis

Study	Bressoux, 2009	Ecalle, 2006	Gerritsen, 2017
Country	France	France	Netherlands
Time period	1991‐1992	2002‐2003	1994‐1995
Grade	3	1	2
Study design	NRS	RCT	NRS
Class size	Mean (SD): 22.9 (4.3)	S: 10‐12, R: 20‐25	Mean (SD): 24.07 (4.5)
Number of students	Total 1,680	S: 570; R: 622	Total 470
Number of classes	Total 100	S: 100; R: 100	NR
Study	Hudson, 2011	Milesi, 2006	Munoz, 2001
Country	USA	USA	USA
Time period	1990	1998‐1999	1999‐2000
Grade	10	KG	3
Study design	NRS	NRS	NRS
Class size	Mean (SD): Reading: 22.61 (6.3); Mathematics: 23.37 (7.1)	S: less than 18, R: 18‐23, L: more than 23	S: less than 19, L: more than 18 (‘usual’ size is 24)
Number of students	NR	Total 11,567	S: 47; L: 57
Number of classes	NR	Total 2,437	NR

Note: KG: Kindergarten, S: Small classes, R: Regular classes, L: Large classes, NR: Not reported, NRS: Nonrandomised study, RCT Randomised controlled trial