The Biting

This week Joel has been biting another child at daycare. 3 times! He bit another child last year around this same time, when he was teething with his 1 year old molars twice. And of course, then, like now, I feared that he would get kicked out of daycare and not grow out of it. But now, what really bothers me is that he knows that biting isn't okay. He will walk around after he's bitten the poor kid and say "NO Biting" and he says "Biting is bad". I'm not really sure what to do. He never bites at home or at church or with our friend's kids. And he has kept it solely to one child at daycare. The one child at daycare whose parents we just happen to be friends with, of course. Joel is much bigger than the other little boy and the child isn't quite mobile yet, whereas Joel resembles a 3 year old. So now I am the teacher with the kid whose parents are called in to figure out what to do. I'm so upset. What do I do? I have a child who knows his alphabet, his colors, and his shapes at 20 months but who is a bully!? Oh, no. Any ideas? Please!!! Look at all these teeth!!