Tough question...
When my daughter was growing up, I was not yet a practicing Orthodox, so there was no intent back then to enlighten my child in faith, except to bring her to a small Ukrainian Orthodox parish in Seattle where she was expected by her mom to learn Ukrainian poetry and dance (well, and also to endure the Divine Liturgy

). Yet, she somehow was growing up very un-receptive to temptations of un-chastity. During her last two years of high school, she had a couple of romantic attachments - but her mom and I never felt any trouble. She was always at home at night, always concentrated on her studies, never lost her head, never participated in any wild orgies etc. We never "taught" her contraception or something, but there was no need.
If she were different and I were Orthodox... I think I would probably *not* teach her artificial contraception. I agree that it's not quite the same to use a diaphragm or a pill versus to go ahead and abort a fetus. Non-abortive contraception is certainly a "lesser evil." Still, I somehow do not see myself as an Orthodox parent participating in a lesson about how to put a condom on a banana, etc. I am afraid that this trivializes marital sexual union, and delivers a message that it's OK (at least safe) to have sex outside of marriage. Being a part of teaching kids that, I would not feel right.
As for "chastising," I really don't know. Perhaps I would not "chastise" my child if I knew that she was having sex as a teenager, but, rather, do everything that was in my power to turn her attention to something different (like... hmmm, studies?), and to convince the other party, the "boyfriend," that what they were doing was not worth doing.