Of course, this theory doesn't apply to everyone, but it is an accepted fact that something as simple as not eating together is a by-product of the family breakdown. Not in all cases, of course.
The other theory, with regard to sport, is that children/teenagers are not able to 'tire themselves out'. Taking part can be a very good way of learning basic skills and has many benefits. Sport or fitness is a form of release. I love the way skateboarders are seen as the dregs of society by the adult population, but in my experience they are actually doing something that they enjoy and have something to focus on rather than hanging about causing trouble.
I agree that fear helps. I was petrified of my headmaster at my Prep-School. He was a lovely man, but he laid down the foundations and boundaries and formed a mutual respect. I would not have dared cross him or some other of the teachers. The sad thing is, there seems to be a severe lacking in support of teachers from parents. I know a fair amount of teachers from my Uni days and the general consensus is that they do not get the support to enforce a strict regime and the classes are too big to make huge inroads.
An excellent post and very good points made.