Maybe he did intend it to be totally educational, but what about how it may have been perceived by other students? He can control his intent, he cannot control others' perception. Los Angeles is a pretty diverse place, and its very likely that other students of different backgrounds may have been frightened or offended by such a display, especially in the current national environment.
one 14 year old in an obviously fake Klan outfit terrifies someone?...even more so in a place that is very diverse?
again, it's about motive here and I suppose a little "time and place" too. Was he just wandering around, doing his daily business in the Klan outfit? Or did he put it on special for the class and took it off when he was done? Neither article I've read/skimmed on it was clear about it. I can't imagine he road the bus wearing it, that sh**t would get you killed in LA.