Finally, the results with weighted cases. RLMS provides weights as one of the variables.
The first sex:
Weighting moves age at the first sex one year greater, 19 rather than 18. But 48.8 per cent of girls starts their sexual life at school. If it starts than it's already late for education, imho.
In other words: the sexuality education must begin at about seventh grade, and instruction in contraception should be a greater part of it.