Hall 2002 (C).

Methods	Cluster‐randomised trial. 2‐arm design with randomisation at school level (60 schools, 30 per arm).
Participants	Children (1201 randomised, 1113 followed up), both sexes (613 female (51%)), aged 6‐19 years (mean of 11.4 years), attending rural informal community schools in the Kolondieba district of Mali. Approximately 20 randomly children (10 boys and 10 females) attending 2nd or 4th grade were selected from each school. Any child with severe anaemia (Hb ≤80 g/L) were excluded. Baseline prevalence of anaemia: approximately 55%. Socioeconomic status not reported.
Interventions	Schools were allocated to one of the following groups: Group 1 (n = 551 at follow up, number randomised not clear): children received 65 mg elemental iron (as 200 mg of ferrous sulphate) and 250 μg (0.25 mg) of folic acid once a week; Group 2 (n = 562 at follow up, number randomised not clear): No intervention. Length of the intervention: 10 weeks
Outcomes	Anaemia, haemoglobin. Results by sex are included in the corresponding subgroup analysis.
Notes	All children in every school were treated for parasitic infections at baseline using albendazole, and vitamin A to treat night blindness. Supplements were given by the teachers and 83% of children were given all 10 tablets and 91% received at least nine tablets. Malaria is endemic in Mali, although the study was done in the dry season when transmission is less intense than in the wet season. Authors provided the ICC (0.0698) and design effect (2.22) to adjust data by the effect of clustering; the estimated effective sample size was used in the analyses.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	60 schools were randomly assigned to either a treatment or a comparison group by using a computer‐generated random number list (information communicated by the author).
Allocation concealment (selection bias)	Low risk	Not reported. Since the intervention was allocated at health care unit level, it is unlikely there was a selection bias at the individual level.
Blinding (performance bias and detection bias) All outcomes	High risk	Participants: Not reported Personnel: Not reported Outcome assessors: Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	1201 children at baseline, 1113 followed up at 14‐16 weeks. (93% followed up). 88 children who did not provide second samples had similar Hb levels at baseline than as those children remaining in the study.
Selective reporting (reporting bias)	Unclear risk	There is insufficient information to permit judgement.
Other bias	Low risk	The study appears to be free of other bias.