This might sound strange, but having new buses and regular drivers on school buses does seem to reduce the problem of unruly kids on school buses. Generally speaking, up until last year, most school bus services round here were operated by First, normally using the older buses from the fleet (Olympians and Deltas). It wasn't uncommon for fights, food fights and other bad behaviour (as well as vandalism) to break out on the buses. As posted elsewhere, I once witnessed the cleanup after an Olympian had all it's upper-deck windows smashed by the school kids on board. There was also a case that the local press made a fuss about when a food fight broke out on the bus, so the driver detoured from the route, drove to the depot and got off the bus, leaving the kids on the bus in the depot until they calmed down. Not to mention that when getting on a bus in the early afternoon you could always tell if it had done a school run in the morning because it would be full of cans, bottles, crisp packets etc.
Since First lost most of the school contracts things changed. Various independents took over the routes, often using fairly new buses and coaches, and all vehicles were a definate improvement from A-reg Olympians. In some cases, the buses usesd are brand new Solo's and MPD's. At christmas some of the buses were even decorated with tinsel etc inside. Did the decorations get ripped down? No. When getting on the buses in the middle of the day do you struggle to find a seat not covered in crisp crumbs and spilt cola? No. Any reported incidents of major fights etc? No. The county council also have a fleet of specially built school buses for routes under their direct control. These routes have regular drivers, and the school kids get to know them. In at least one case, the driver asks the older students to keep an eye on the younger kids, both looking out for them in case they get bullied and to stop them misbehaving. If they do start misbehaving, he asks the older ones to have a word with younger ones and ask them to stop.
So whilst it may at first sound stupid to throw new buses at school routes, it can actually be a lot 'cleverer' than you think.