haha, yes, far cry 3, the game about embracing your inner murderer which culminates in a brutal double-murder / rape... fun for the whole family

@240
funny you should bring up the "teacher" thing because rockstar (guys who made gta) made an "open world" style game called "bully"... set in a school. perhaps not the MOST kid-friendly game, but it's rated teen, as opposed to mature, if that gives you any idea of the world of difference between it and GTA. it's for ps2, pc, and current gen consoles. speaking of last-gen consoles, theres a hulk game for gamecube which would probably be perfect (if you have a 'cube).
you might also try something like infamous, if you have a ps3, which is definitely violent but far less so than gta (more in line with a typical mainstream shooting game... not a "boundary pushing" one). always mentioned in the same breath as infamous is "prototype", which is a bit more violent, but more akin to super hero violence than realistic "im going to fuck your face with a bat" violence.
you could also look into the crackdown series. while for all i know its chock full of profanity/violence, the graphics are pretty cartoony and i'd be kind of surprised if it was too over-the-top.
the "just cause" series is, from what little i've played, far less focused on extreme violence, sex, etc. than gta and offers even more exploration / blockbuster-movie style adventuring.