The caption to that pic had this "OH MAI GAWD YOUR FRIEND CAN MULTIPLY AND DIVIDE?????".
Pretty stereotypical stuff. Now the only question you really have to ask yourself is this. If you were a teacher and there was one black student in your class, would you have used the pic?
I didn't think so.
Does race have to color every single thing we do?
Isn't it possible that the guy saw a picture and thought it applied to his situation, and didn't think about race in the slightest?
I was guilty of the same thing a few months back - in a thread on Michelle O'bama, I posted a celebrity-morph picture where the pic was morphed into a chimp face. The cry of racism was immediate and I asked to have it pulled. It didn't dawn on me that anyone would interpret it that way, but that's what happened.
The fact is that people don't think about race nearly as much as the victims imagine. The idea that it's not "safe to go back to school" is just ridiculous.
I think this was clumsiness, not malice.