Both schools and family have a big part to play. Family needs to instil self respect, not just parents, as some parents are hopeless and abusive themselves, but the wider family! Schools should also do a lot more to deal with bullying and abuse within the school gates. Lack of self respect is the key problem and if parents/family aren't teaching their daughters/nieces etc about self respect, wellbeing, etc., then the schools need to offer support and guidance to make up.
Parents/family/schools also need to advise against peer pressure. I.e. where a girl is pressured to have a boyfriend/have sex, etc., because all her "friends" are doing it. That comes back to self respect too, of course. There needs to be a strong message that not having a boyfriend, not having sex, etc., is actually OK!
It's the "I need a boyfriend" mentality which I think is almost self destructive - some girls will "accept" anyone, even the obviously unsuitable/abusing boyfriends rather than not have one! Not because they actually "want" a boyfriend, but the peer pressure etc.
I'm actually glad that being gay is far more accepted these days, as it breaks the "mould" and expectation of teenage girls having to have a boyfriend, any boyfriend. Not just for the gays themselves, but also for everyone, as there's less pressure to be on the arms of a boy when friends have girlfriends - a complete change of the dynamics of going out, hanging out, pubbing/partying when not everyone seems to have to be a traditional "boy/girl" couple.