Parents should teach their kids about sex (and marriage, and love). It's time to take the sex stuff out of the schools. Parents abdicated the sex-ed responsibility, and this is the result. Time to be parents again.
My opinion is that parents have abdicated more than just sex-ed...they have abdicated being parents. I sincerely believe that the majority (not all, of course) but the majority of parents who have their kids in public school will not do anything to "rock the boat". They have what is basically free childcare. They don't care what their child is taught, just so they are out of their hair long enough for them to do their own thing.