I would not call your son naughty. They don't understand the difference between doing something wrong and being a naughty person (maybe I read your post wrong on that one). Make sure you clarify that his action was something he should not have done (say "we DO NOT bite others"), validate his feelings (I understand you were frustrated but next time...), and follow through with a consequence (don't threaten to take something away - take it away). May not do any good by the time you get home though. It's too late by then.
Make sure the school follows through with a consequence right away. If my sons school put my DS in the corner I would pull him from that school. They can use a time out or better yet take him away from others and toys for a time out. I do not like humiliation as a punishment. I prefer natural consequences. You bite your friends, you do not get to play with your friends.
Tell the other parents you are sorry and you talked to your son about it and that it should not happen again. There is not much more you can do. They will either have to get over it or not. I am sure their kids have done less than desirable things at times also. Comes with the territory of being a parent.