I have no idea which parts of London you travel by bus on, New Judge, but I haven't seen people walking (which is good exercise anyway) rather than use the bus because of badly behaved children. Round our way some people may well walk during the times when children are travelling to and from school, but during school holidays and outside of those times during term, people still catch the bus.
My own experience is that the children, during term time, can be a bit rowdy, but beyond that they seem to behave reasonably well. The local schools make sure there are teachers out in the main part of town and at the mainline and tube stations before and after school, and the children are disciplined if they are seen to be causing trouble.