Well maturity is something that isn't really tangilbe, thus so it is hard to measure.
I mean, you got two main factors, your age and your enviroment.
Though, from a more general standpoint I'd just say that if you go as far to purposely make other people mad, don't do it.
Though you're only 13, so that's pretty much common place and is probably actually needed for other kids to pick on others as it does teach one how to ignore people.
Regardless of all that, you're find. Don't queston your maturity, and though I won't win any alcolades for this, you are only 13.