I transferred from a public school to a Christian school last year, and at that Christian school I was taught all about the Crusades and how awful they were. What we weren't taught about were people like Stalin, Mao, Pol Pot, etc., etc. Funny how that works, isn't it?
EDIT: The social studies class I took was called "Global Issues". It dealt with things like poverty, world hunger, terrorism, deforestation, global warming, war, drug trafficking, etc., etc. - issues that are currently affecting the world negatively today. (Hence the name "Global Issues".) I did, however, learn about the crusades in my religion class. It was called "Church History". You can't very well learn about the history of the church without learning about the Crusades, now can you?