Sample size Sample size calculation is performed by WinPepi software with the assumed anemia proportion of 25% and 50% in arm 1 and arm 2, respectively (5% significance level, 80% power, and 1:1 sample size ratio). Required sample size would be 58 school-age children per arm. We will recruit115 school children after considering design effect of 1.5,and drop out level of 10% and sample size for malaria incidence