I'm not so sure. In my second grade classroom, both boys and girls have parents who want them to succeed and who enforce high expectations at home. The boys swear, throw chairs at least once a week when they're angry and fight. The girls cower for their lives. No conditioning here. Just more violent, immature, and underdeveloped pre-frontal cortexes, as far as I can tell. (To be fair, over of the girls throws chairs too).