The legal consenting sex age is 16....but who is going to know? It doesn't matter in terms of legality. The worst that will happen is they will be dubbed promiscuous.
I'm guessing that you are the 13 year old girl. That's kinda gay..I bet you don't even really know what it is or how to do it. You shouldn't be doing that with a guy that you aren't in LOVE with. And don't be all like "oh i am in love with him' your 13 and still in middle school. I don't get why kids think they are so grown up now, it's kinda pathetic.