It would help behavior and discipline problems that some children don't seem to get given by their parents. Im sure it would also help with the litter on buses and smoking that the bus drivers find hard to control by themselves. The passengers would feel less intimidated as there is no one to support them when the groups of children are quite large at the back of the bus.
It would help with space on buses and cost waste.
It would also help tourist areas and London as a whole as I have seen different abuse by passengers against different races of people – sometimes because there are not strong enough bus rules.
Such as giving up seats, push-chair rules and wheelchair rules.
A rubbish bin on buses would also help.