Yes because its the states job to teach children things that parents should.
It's the government's job to ensure that children are educated, particularly about such dangerous things as love and drugs.
And there are a number of families who don't bother to teach their children about safe-love, or they don't know enough about it or they don't know how to teach their children about it.
No right-minded government wants lots of under-age pregnancies and lots of deaths due to STD's.
That's why it's taught in school as it should be.
And in England it is taught in every school normally from atleast Year 5 and up, but sometimes (as in my school) from Year 4 and up. (Especially in my old school as it was claimed numerous times (although I'm unsure as to the validity of this) that our town happened to have the highest rate of teen-pregnancies in the whole of Europe by population)
And it is taught every single year in compulsary education since they first teach you.
And even when you get to optional education like I am, they still go on about safe-love and they actively give out guidance and contraceptives.
Anyone who thinks it is stupid for them to teach you love education in school is an idiot in their own right.