My guess is that while some feminist have included men and boys, the boys have less incentives for change. I mean, when my brother was a teenager, he associated with other boys who weren't taught at feminist houses. That mean that he picked up on sexist things from his friends and there was "rewards" for defending sexism. Sure, he later grow up and became feminist too. But for boys there is an inmediate reward for being sexist at school, it puts you above all girls instantly without any effort, make you accepted in the group and also allow you the "boys would be boys", which means more freedon and a pass to do certain things that are wrong. It is like a "free of jail card" for free. Plus being able to not do domestic chores, have more free time, etc.

The problem is not so much that feminist haven't taught their sons, it is that boys also learn from other people and see the inmediate advantages of sexism, while the disadvantages are not that obvious on first sight. They might catch on that later on life.

But there are some feminist boys and teenagers. Change would come.