We home schooled for seven years. Now six of our kids are in charter or public school -- the oldest in 7th and 8th grades. We're thrilled with 99% of what goes on in the school we're so fortunate to have. But on the other hand, oy-oy-oy-oy-oy. It is a tricky age.
It's our job to meddle in our children's lives. You don't have to be an obnoxious helicopter parent to realize that kids in their early teens are not yet adults. We're not done raising them yet! And kids in home school or Catholic school face many of the same challenges our public school kids do.
The first area of concern is the other kids. We've never had to flat-out forbid our kids to hang around with a particular friend; and such an edict would bring out the rebellion in some children, anyway. But kids that age are horrible at recognizing their own motives when they make friendships, so it's helpful be frank and point out to them that they seem unhappy when spending time with so-and-so, but that they seem to have a lot in common with so-and-so -- hey, let's invite her over this weekend, etc.
We have also told them repeatedly that, as Catholics, it's their responsibility to be the good guys, even if it makes them feel like dorks or jerks. This means that if someone is doing that idiotic dare they saw on YouTube, they have to be the ones to tell the teacher, or at least us. (Whether they are following through on this, I have no idea. But at least they know that they ought to do it -- that it's not noble or courageous to keep dangerous secrets from adults.)
We try to avoid freaking out when we do hear something alarming, so that the kids will be more likely to tell us stuff in the future. (I routinely fail at not freaking out, but it's a good theory, anyway.) I do make a huge effort maintain a good chatting relationship with the kids, so that we have some idea of what their days are like. If something sticky does come up, there's at least a chance that they'll bring it to us.
They also know that it's their responsibility to keep conversations clean. Depending on their temperament and their place in the pecking order at school, they may be able to actually steer the conversation away from dirty topics. But even if they can't, they need to understand that listening quietly is still participating. If they can't change the subject, they need to get gone. (Kids that age can be conveniently naive about personal responsibility, and let themselves off the hook very easily.)
But they do need to talk about sex at some point. Whether you home school or work with a teacher, they need to learn positive information, not negative; otherwise they'll fall for the old cliché, "How can it be wrong when it feels so right?" Here's the thing: most of what the world teaches is actually negative, despite the happy talk about freedom and fulfillment. People who consider sex to be a gift and a blessing do not use words like "safety" and "protection!" Kids need to learn that sex is a gift and a responsibility, one which is fruitful and joyful within marriage. And they need to learn that HPV and single motherhood are the fruits of sin, not the manageable side-effects of normal behavior.
In the mean time, we are very fortunate that their teacher is forthcoming about what goes on in the classroom, and we trust her to respect our parental authority, even if she doesn't share our religious principles. We're content to let someone else teach the kids about the biology of reproduction, but it's our job to teach them about the social and behavioral aspects of human sexuality. We are in close contact with the teacher about what will be covered in class, and will be stepping in, opting out, and providing alternative lessons when we need to. (More later on programs and materials which introduce kids to the Theology of the Body.)
We're lucky that our school even acknowledges the need for parental involvement. We've all heard stories of schools encouraging kids not to tell their parents about what they discuss in "health" class, or of parents hearing about questionable material only after the fact.
It is entirely appropriate for kids this age to have questions about sex. Parents are responsible for overseeing the conversation, no matter what their schooling situation. The key here is relationships: (1) having a good relationship with your kids, to make it possible to talk about these things; (2) having a good relationship with your kids' teachers, so you will be in the loop if you do have concerns; and (3) always conveying to your kids that sex is about relationships, whether those involved recognize this or not.
Kids have to grow up and make their own choices eventually. We owe to them to educate them on what their choices actually are, and to remind them that they have the responsibility to be strong in a world that assumes they are weak.