it wasn't the teacher's place to give that "lesson". and, based on what i get from the article, the way she delivered the message to the boy wasn't the most effective means. for one, it rates him as second class automatically which could stigmatize the boy in the future. in my humble opinion, by her even mentioning race and saying he needed to work harder because of it puts him in a position where he feels like he needs to seek approval by any means based on his race, which he shouldn't have to. he shouldn't be seeking anyone's approval. if he does his assignments correctly and to the best of his ability, that's what's needed. he doesn't need to have the idea that he's seeking approval hanging over his head. nor does he need to have it come from someone he'd be seeking approval from either, seeing how she's a white teacher.
it just shifts his mentality in a way that wasn't necessary, making him believe he has to work hard solely BECAUSE he's black, which isn't true. he'd be working harder to gain the approval of those who aren't. either way, that wasn't something she needed to tell him. it wasn't her place and was inappropriate. even if you feel like it's true or not. and that doesn't mean that i don't think what she said is true either...