See my post #27. Don’t be so hovering/strict to your kids that once they leave the coop they go helter skelter wild...again, I saw it a million times while at uni.
It's great supervise to your kids but when you jump in front of the TV you are waiving the forbidden fruit in front of them making them more curious about it. It's a tricky situation to handle. You want to make sure they understand the consequences of sex.
I remember a kid whose parents would allow them to eat candy so whenever she went to a friends house she would stuff herself with ituntil full being that it was a rare experience.