The problem with your idea is that many children of 11-12 are already into puberty. There would be even more sexual encounters without sex ed. One doesn't normally learn how, for the first time, in sex ed. Most 11-12 year olds already know how.
There is no better love between 2 people than mutual respect for each other WT Young, 2002
Who gave anyone the authority to call me an authority on anything. WT Young, 1969
Since Evolution is only ~90% correct it should be thrown out and replaced by Creation which has even a lower % of correctness. W T Young, 2008