If any history teacher is teaching that then he needs to be fired. I explain to my students that history education progressive in a way similar to movie ratings. When you are in elementary school you get the nice G rated, happy ending, history (Thanksgiving, Columbus, Lincoln freed the slaves, etc.). Middle school is PG. You start to see some of the ugliness, but its only suggested at, not overtly shoved in your face. You are also given some limited opportunities to draw your own opinions. High school is still only PG-13. This is often up to the teacher. Many teachers fear going beyond the textbook because of ignorant parents and administrators, who themselves probably never went beyond PG-13. College runs the gamut from G to XXX, depending on the professor and the school. Also, what you are taught usually depends on the professor's political leanings (typically liberal, but not always).