I think that they behave in such a way because they think that he is just a bus driver so they think it not important to behave politely with him and not give them respect , it may be that they also think that they are of high standard and he is of low standard. I would give them the advice to talk and behave politely with him and give him respect though the driver would be of low standard and would not be rich but he is older than us so we should behave properly with him.