As said above it could be many things. Could be that he does like you but his mates are giving him stick about it, you know what young boys are like.
Alternatively maybe he isn't feeling to good about something atm, meaning he lack the confidence to talk to you.
It's fairly normal for boys, they normally have a hard time showing how they feel, especially if he does like you and he is a afraid you wont feel the same way. You could always try and drop hints that you do like him (to him) and he might gather the confidence to say something.