Yet, for hundreds of millions of young people, these basic building blocks are not in place. Staying in school means both boys and girls are less likely to have sex. The longer a girl stays in school, the greater the chances that she uses modern contraception if she does have sex, and the lower dieir chances of giving birth as an adolescent (Greene et al., Most of these children are never expected to enrol, and in sub-Saharan Africa, most are girls. (