Speaking as one who used to do the same, its a mechanism boys sometimes use to make contact with a girl they fancy without actually telling her. Most of us are cowards when it comes to showing our feelings, not just to the girl but in front of our mates. The reason is that if a boy did tell you and you rejected him, his mates would tease him even worse. Off course they could be teasing you because they are idiots, but my guess is that one of them fancies you. Just smile and say nothing. Remember, in the caveman days they used to hit them over the head and trail the girl into the cave. So maybe your lucky. Ha ha