The only issues we've had is with other kids in the high school. His school bike cost me £50 and another £50 or so to replace the chain, shifters and freewheel. It is a Ridgeback MX24 which has a retail of over £230 so is decent, but it's a matt grey so doesn't stand out. At school though, the bike has been kicked by other kids, and we've lost a decent d-lock after my son forgot to lock the D back onto the sheffield stand, so the kids chucked one part of the lock, leavig the locking mechanism. Since then we just use a basic Knog cable lock - secure enough as the cycle shed gets locked during the school day.
The bike has had the odd mechanical - usually shifting off the front granny chainring as they are cheap mechs, but my son hasn't yet got the hang of putting the chain on - usually ends up in a rant as his other bike doesn't do that (also much more expensive and newish).