I disagree, at this stage one's sexual feeling are beginning to do all sorts of new things. While it might not be best to run round having sex with others, there is plenty of self discovery on personal feelings.
As Kasic said it really comes down to how their parents would react.
There is plenty of time to do it later. Right now you're 13, just entering puberty, and possibly the more important phases of schoolife that can make or break your future. You don't need to explore your sexuality, just think about it from time to time, and not stress so much over it.