When being shy around boys you generally cant think of anything to say to them.Try being Spontaneous, start a conversation with them about the first thing that pops into your head.
Also bring up conversations that you're comfotable with. It takes alot of courage to start a conversation when your shy.Dont worry if you think its silly or random. Random is good. Dont forget most importantly be yourself, also dont worry to much about what they think of you. They should like you for you.
Like somebody else said "dance". It's fun and a great way to losen up.
Try to forget that your shy. If you keep thinking your shy your going to stand there giggling and not saying much. Even if its just talking to them here and there. It will build up to a normal conversation, like one you would have with the girls.
It does take sometime but if you do some of these things you might be able to come out of your shell
hope this has helped.