3. Characteristics of participants in each study.

Study	Location	Group N°in analyses	Age	Gender	IQ	Ethnicity	SES	Inclusion criteria	Exclusion criteria	Population
Barker 1995	USA	Intervention: 18 Control: 18	Mean not reported SD not reported Range 6.2–7.8 years	Not reported	Verbal Mean 16.5 SD 2.36 Range 11–22	Not reported	Not reported	Students nominated by teachers from 2 elementary schools who were given a short series of pretests assessing phonological awareness skills and basic word recognition skills. These children were then given further 2 tests and those scoring below the 40th percentile and the 50th percentile on the subsequent test were selected.	None stated	First‐grade students
Blythe 2006	Australia	Intervention: 10 Control: 10	Mean 101.5 months SD 17.58 months Range not reported	Male: 75% Female: 25%	FSIQ‐2 Mean 100.15 SD 9.38 Range not reported	Not reported	Not reported	Children who received group‐based remedial reading instruction at school and were referred by a support teacher.	After referral children completed the WISC‐III FSIQ. Those who scored < 20th percentile were excluded.	Dyslexic primary school students
Chen 2014	Canada	Intervention: 9 Control: 9	Mean 7.06 years SD 0.24 years Range 7–8 years	Male: 39% Female: 61%	Mean 19.79 SD not reported Range not reported	Bilingual speakers of English and French	Not reported	Students considered to be 'at‐risk readers' who fall 1 SD below mean on the GRADE (standardised test)	None stated	Second‐grade students
Ford 2009	USA	Intervention: 9 Control: 9	Mean 16.18 years SD not reported Range not reported	Male: 55% Female: 45%	Not reported	22% African‐American, 67% Hispanic, 11% White	Lower	Students who were enrolled in the remedial reading programme were invited to participate. Below mean reading skills were based on the ISAT.	None stated	Teenagers enrolled at an alternative high school, that is, a high school for non‐special education students or students at risk of dropping out.
Hurford 1994	USA	Intervention: 25 Control: 25	Mean 80.35 months SD not reported Range not reported	Male: 48% Female: 52%	Mean 90.37 SD not reported Range not reported	92.8% white, 6% African‐American, 5% Hispanic, 7% Asian‐American	Middle	Classification data from Hurford 1993 was used with more relaxed criteria for eligibility, that is standard scores in reading of < 91 were included rather than < 86.	None stated	Children at risk of reading disability
Hurry 2007	UK	Intervention: 92 Control: 43	Mean not reported SD not reported Range 6–6.6 years	Male: 61% Female: 39%	Mean not reported SD not reported Range 92–96	16% spoke English as a second language	42% of the sample were eligible for free school meals.	In 63 schools, the 6 poorest year 2 readers were selected on the basis of their Diagnostic Survey (Clay 1985) performance. Of the 22 schools using Reading Recovery, the poorest scorers were offered intervention.	The remaining children, that is, those less poor at reading then those that were selected for the experimental condition, were assigned to a within school condition.	Children with reading difficulties
Levy 1997	Canada	Intervention: 75 Control: 25	Mean not reported SD not reported Range 5.9–7.2 years	Male: 48% Female: 52%	Not reported	Not reported	Not reported	Children were given word reading tests, children that read < 7 words on any of the screening tests were selected.	None stated	All children from Grade 1 and senior kindergarten from 2 schools, whose parents consented to their participation.
Levy 1999	Canada	Intervention: 64 Control: 32	Mean 7.7 years SD not reported Range not reported	Male: 56% Female: 44%	Non‐verbal Experimental group: Mean 10.88 SD not reported Range not reported Control group: Mean 10.65 SD not reported Range not reported	Mixed racial distribution	Covers all SES	Children were given a word identification test (WRAT‐3), if they scored < 90 they were given another word identification test (WRMT) and if they read below half a grade below their grade level and read no more than 15 of the training words then they were included in the sample.	None stated	17 schools participated in the screening process with permission for participation obtained from the board, schools and a parent or guardian
Lovett 1990	Canada	Intervention: 18 Control: 18	Mean 8.4 years SD 1.6 years Range 7–13 years	Male: 70.4% Female: 29.6%	Verbal Mean 98.4 SD 10.6 Range not reported Performance Mean 106.2 SD 12.6 Range not reported	Not reported	Middle	Children had to score < 25th percentile on at least 4 of 5 reading measures used in the screening test and have at least low mean intelligence.	Children with English as a second language, history of extreme hyperactivity, hearing impairment, brain damage, a chronic medical condition, serious emotional disturbance, or attention deficits.	Children referred to the Learning Disabilities Reading Program.
Lovett 2000	Canada	Intervention: 51 Control: 37	Mean 9.9 years SD 1.6 years Range 7–13 years	Male: 68.1% Female: 31.9%	Verbal Mean 92 SD 13.7 Range 58–133 Performance Mean 98.7 SD 14.3 Range 63–136	Not reported	Not reported	Children needed to demonstrate a 'substantial underachievement' on 4 of the 5 reading based screening assessments.	None stated	Children with severe reading disabilities that were referred to the Clinical Research Unit for remediation.
McArthur 2015a	Australia	Intervention: 39 Control: 39	Mean 9.42 years SD 1.71 years Range 7–12 years	Male: 63.8% Female: 36.2%	Non‐verbal Group 1: Mean 97.50 SD 14.16 Range not reported Group 2: Mean 95.56 SD 17.12 Range not reported	Not reported	Not reported	Children who scored below the mean range for their age on the Castles and Coltheart irregular word reading test and/or non‐word reading test.	History of neurological or sensory impairment; non‐English speakers.	Children with reading difficulties
McArthur 2015b	Australia	Intervention: 46 Control: 46	Group 1: Mean 9.53 years SD 1.51 years Range 7–12 years Group 2: Mean 9.58 years SD 1.45 years Range 7–12 years	Male: 46.3% Female: 53.7%	Non‐verbal Group 1: Mean 97.02 SD 15.75 Range not reported Group 2: Mean 95.57 SD 1.65 Range not reported	Not reported	Not reported	Children who scored below the mean range for their age on the Castles and Coltheart irregular word reading test and/or non‐word reading test.	History of neurological or sensory impairment; non‐English speakers.	Children with reading difficulties
Savage 2003	UK	Intervention: 78 Control: 26	Mean 5.9 years SD not reported Range 5–6.3 years	Male: 60% Female: 40%	Not reported	Not reported	Not reported	Over 2 sessions a series of reading‐ and spelling‐based assessments were used to find the poorest readers in year 1 of the school. The lowest performers were recruited.	A teacher identifying a child as being too immature to deal with working in small groups.	Children with the lowest reading performance for their age within a Local Education Authority or School District
Savage 2005	UK	Intervention: 26 Control: 26	Not reported	Male: 50% Female: 50%	Not reported	Not reported	Lower	Over 2 sessions a series of reading‐ and spelling‐based assessments were used to find the poorest readers in year 1 of the school. The lowest performers were recruited.	None stated	Children with the lowest reading performance for their age within a Local Education Authority or School District

FSIQ: Full Scale Intelligence Quotient; IQ: intelligence quotient; ISAT: Illinois State Achievement Test; SD: standard deviation; SES: socioeconomic status; WISC: Wechsler Intelligence Scale for Children; WRAT: Wide Range Achievement Test; WRMT: Woodcock Reading Mastery Test.