Is it rude to ignore someone when they congratulate you?

They might have been being mean. Young immature people are just that way sometimes. What you should do is just wave and smile a big fake smile. That way, you aren't being rude or put down either way. Don't say anything, just show them you acknowledge them. You never know, they might be trying to be nice. You could end up making friends with some of them. Just be careful and don't get involved in anything bad.