Sample size
We calculated sample size based on the effect size of 20 percentage point using the formula of sample size estimation for conventional cluster randomized control trial. After considering the design effect of 1.5, 80% power, and 5% attrition rate, the desired sample size was 148 in each arm. Since we had two schools in each arm, our estimated sample from each school was 74 girls. Thus, to reach the desired sample size we collected data from 25 girls from each grade in a school (a total of 75 from each school and 150 from each arm).