Look, I'm no fan of modern schooling (public or private), but this is pretty ridiculous.
Bullying: I was bullied far more by the neighborhood kids than anyone at school. YMMV of course, but that's exactly the point -- kids are kids, and leaving the school building doesn't change that. Blaming school missing the point.
Also, RE: churches, they're one of the few widespread institution where it's not abnormal for adults to gather and condemn people who are different (LGBT, non-sexually-repressed). It's just that churches have a much better grasp on socially appropriate rhetoric (not "faggot!" but "sinful lifestyle", not "slut!" but "you must save yourself for marriage". It's more subtle, but the intended effect is the same: otherizing people who are different from or disagree with the in-group and shaming them into conformance).
If your child is gay, the local church youth group is very likely one of the most intense bullying experiences that child will ever experience.
Sex: Teenagers are going to know and think about sex. Consider e.g. religious events for adolescents, which often explicitly discuss sex in a very moralizing way. In fact, IMO, having attended one, American conservative christian youth groups are one of the least healthy places to learn about sexuality.
Weapons: I've been in a lot of schools, and in every single one of them, anything as much as a pocket knife was a huge deal.
Drugs: Again, far more likely to encounter these hanging out with the neighborhood kids than in the (incredibly risky) setting of a modern school. Even the more die hard pot heads are rarely stupid enough to bring their drugs to school.
So if "bullying, sex, drugs, and weapons" were my greatest fears, I'd probably lock my kids in school 24/7 and never let them play in the neighborhood without adult supervision.
>...I don't think children will lose much socializing without schools.
I don't think children necessarily have to lose much socializing without schools. But the anecdotal evidence I have suggests that providing sufficient socialization is much harder than it sounds.