Okay, as an immigrant to America, I find this completely stupid. When I was a student a couple years ago, we were learning about 1st amendment rights. I'm pretty sure that Freedom of the Press applies to this. He is simply expressing himself differently. If a teacher came up to me and said, "Girl, you can't wear that Rise Against shirt because it represents an insurrection (I live on a marine base, mind you)," I would get unbelievably pissed off. Sure, Rise Against is a political band vying for change. But they aren't vying for change in only America. They want it everywhere. In no way does it make me want to rebel against the American government.
So, using that as comparison, if a second grader wants to paint his face black in honor of Martin Luther King Jr., then let him do it! It's not as if he's going around using racial slurs and portraying African Americans and black people in a bad light. MLK was a great man for American society, and the country would not be what it is today without him. Hell, without him, Americans would have moved on from African American discrimination and gone to Latino discrimination or Asian discrimination, or even European discrimination. It just gets me so riled up that a teacher filed a complaint without first getting the entire story, without asking questions. But noooo, we just had to go and say, "I don't like this kid because he painted his face black." Makes me want to go over there and punch that teacher in the gut, damn the consequences.