Stuart Biegel, a professor at UCLA, and the author of the new book The Right To Be Out, gives a reasonable answer in an interview with Salon:

But surely, the culture as a whole has also become far less homophobic than before.

It is on the wane, and you see a lot of data supporting that. But there has been something of a backlash in some places, in light of the sea change in legal recognition of same-sex relationships over the past decade. When Howard Dean signed the first civil union legislation in Vermont in 2000, people couldn’t believe it. Ten years later we have civil unions in eight or nine states and legal marriage in nine or 10 countries and five states, including Canada, D.C., Mexico City. This amount of change is unsettling for a lot of people, and the schools are a place where a lot of these values issues are heavily contested. In a number of schools, at this point, we see a situation that might actually be worse than 10 years ago.

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What determines whether a school is gay friendly or non-gay friendly?

A lot of it has to do with the school culture as it’s evolved over time and a lot of it has to do with whether a school is known to be a sports school. While sports can be incredibly beneficial, in many cases school athletic departments have the largest percentage of homophobia of any department in the school, if you can characterize it that. The leadership of the school as a whole can play a key role: whether the school focuses at all on school climate, on issues of respect and not tolerating the word gay as a pejorative term. But it’s not static, and there’s a tremendous amount that individual educators can do here.

The interviewer, Thomas Rogers, also points out the recent study which shows that, though gay kids are less likely to misbehave than their straight counterparts, they’re punished at a far higher rate.  That, dears, is called institutional bullying, and when adults model the behavior, children learn that it’s okay.  That’s why the only appropriate reaction when Religious Right gasbags hit the fainting couch at the suggestion that their “Biblical morality” has something to do with why kids get bullied to death, is to simply refuse to entertain their faux-concern and say something like “Oh, do shut up and eat the sandwich you’ve been making ever since Anita Bryant started talking.”