Parents have raised concerns about pupil overcrowding on school buses
Parents claim that up to 20 children often have to stand
In some cases students say buses are tilting heavily on corners because so many of them are having to stand.
There have been calls for the First bus company to put on extra vehicles to serve routes going to Coombe Dean School.
The firm admits there is a problem on some routes, but says without extra funding from the school or the council, it cannot provide more vehicles.
Students claim there are two buses which are particularly badly affected.
One pupil said: "There's been loads of people packed in and people standing upstairs and I don't think they're supposed to."
Amanda Harrison, whose son goes to the school, said: "The bus is very overcrowded and sometimes I'm very, very worried he's going to miss the bus and there won't be any other buses to pick him up and he will be stuck there.
"Last week the bus was tipping because it was very overcrowded and when it was going round corners it was actually swaying."
In a statement the company said it was trying to resolve the situation and agreed there were too many children travelling to Coombe Dean School and not enough space on the two buses to take them.
Putting on another bus would not be commercially viable, it claimed, adding that it could only "consider allocating another vehicle to the service if there was significant financial support from the school or the council".