Some notes on gender and children's literature:
My assertion: The absence of strong female characters in children's literature is irrelevant to the children reading it UNTIL the children are told by society that their gender differences are the most critical things about them.
For boys, that's pre-puberty. For girls, it's puberty. Until we start to get boobs, we can do and be anything or anyone. Harry Potter? You bet. One of the Stone twins? Sure thing! They're fun, they're smart, and they give good one-liners.
Give a copy of 'Have Space Suit, Will Travel' to a nine year old girl, and she's going to identify with Kip just as strongly as her 8 year old brother does. Not Peewee. Kip. Kip, like many of Heinlein's young heroes, is a boy scout ideal incarnate: smart, honest, dutiful, eager, and, you guessed it, well prepared.
To a young girl, the fact that Kip is a 'he' is irrelevant. He's just part of a great adventure story that you can come along on. Gosh, why would gender have anything to do with it?
It isn't until that same girl hits puberty and becomes suddenly, more importantly than anything else, FEMALE, that the omnipresence of boys as protagonists in children's literature becomes a significant problem.
It is then that the lack of female role models becomes a critical lack, as girls are told that they are DIFFERENT from boys, that they are OTHER. The inference drawn from that information, that wedge driven between boys and girls, is that boys as role models are no longer appropriate. And then a girl turns around, looks at the literature presented for consumption, the TV, pop culture as a whole, and says 'well, if I'm so different, where's the stuff that's just for me?' Where are the strong female role models?
And, of course, there are very few to be found.
No wonder we get depressed during adolescence. We look upon the wasteland, and it is for us.