Table 3

Individual study and combined effect sizes (SMD) for arithmetic, reading, spelling and SEN (RR)

	Arithmetic				Reading				Spelling				SEN
Study	SMD	SE	z	I²	SMD	SE	z	I²	SMD	SE	Z	I²	RR	95% CI	z	I²
Assel et al22	−0.36	0.13	−2.74**
Cheong et al31	−0.74	0.12	−5.92***		−0.41	0.12	−3.40**		−0.55	0.12	−4.46***		2.52	1.45 to 4.40	3.26**
Clark and Woodward32	−0.66	0.14	−4.65**		−0.65	0.14	−4.60***		−0.56	0.14	−3.96***		1.95	1.25 to 3.05	2.92*
Frye et al20					0.55	0.13	−4.16***
Hutchinson et al33	−0.58	0.11	−5.36***		−0.50	0.11	−4.67***		−0.50	0.11	−4.67***
Johnson et al24	−1.46	0.12	−12.31***		−1.06	0.11	−9.40***						5.55	3.49 to 8.81	7.25***
Litt et al34	−0.61	0.12	−5.03***		−0.36	0.12	−2.98**						5.06	2.83 to 9.05	5.48***
Loe et al23					−0.47	0.20	−2.41*
Luu et al16					−0.78	0.11	−6.91***						2.88	1.86 to 4.45	4.74***
McNicholas et al35	−0.91	0.21	-4.32***		−0.43	0.20	−2.12*						2.75	1.15 to 6.61	2.26*
Northam et al36					−0.59	0.24	−2.49*		−0.59	0.24	−2.49**
Rose et al17	−0.42	0.19	−2.26*		−0.36	0.19	−1.94
Sayeur et al37					0.04	0.45	0.10
Short et al18	−1.02	0.13	−7.66***		−0.54	0.13	−4.20***						1.72	1.17 to 2.51	2.79**
Simms et al38	−0.63	0.15	−4.16***
Taylor et al39	−0.51	0.13	−3.95***		−0.30	0.13	−2.32*		−0.54	0.13	−4.19***		2.02	1.47 to 2.79	4.31***
Taylor et al40	−0.63	0.14	−4.42***		−0.51	0.14	−3.63***		−0.45	0.14	−3.18**		4.56	2.12 to 9.78	3.89***
Summary effect	−0.71	0.09	−7.67***	81.91	−0.44	0.10	−4.38***	86.27	−0.52	0.06	−9.53***	0.00	2.85	2.12 to 3.84	6.90***	69.46

*p<.05; **p<0.01; ***p<0.001.
RR, risk ratio; SEN, special educational needs; SMD, standardised mean difference.