Eich, I know this has nothing to do with a principled person like *you*, or presumably most young men you know. But there are plenty of reasons for girls to be afraid of boys. Mostly in unsupervised venues, not somewhere like a classroom -- but once that instinctive fear-of-predators reflex kicks in, it's hard to disarm. (And I imagine that someone who grew up with only sisters, and went to a single-sex school, wouldn't have had a lot of opportunities to build friendly, nonthreatening relationships with boys. I at least had brothers and classmates.)
That's not to say girls can't be nasty, bullying, or even physically aggressive -- but *on average* girls don't pose the same threat to a guy on his own that a group of guys do to a girl.
I got bullied a lot in junior high, including one incident of what nowadays would be considered sexual harassment (maybe even threatened assault).
I don't think my tormentors (boys my own age) would have actually laid a finger on me... but I say that now as a big, tough grown woman who's capable of looking people in the eye and employing the art of verbal self-defense. Back then I was a timid 13-year-old who looked about 9, and some crude talk was enough to absolutely terrify me. It took me a good many years to get over the stereotype that "Boys = Scary."
(It also helped that I went to a women's college, where we didn't have to deal with a lot of the party atmosphere that goes on at fraternities and sororities, or the idea that there's something unseemly about girls being interested in technical subjects or being leaders. Blessedly, a lot of the latter prejudice seems to have disappeared since I was in college.)
I should add that the vast majority of men I've ever crossed paths with are fine, honorable people who'd find it unthinkable to take advantage of a woman, no matter what the setting. But it only takes a few bad apples...
Hmm :/ the first and only boys I ever knew were horrible for 8 years, then I went to a girls school for high school, which was better (but girls can be mean too) and when I started college (co-ed) I'd thought that boys would have grown out of hair-pulling etc...buuuuuut, they hadn't. Which is actually why I have a bob haircut now instead of a ponytail -___- but it solved the problem, and it doesn't look bad, heh.
And they had creepier motives than in primary school too. :/