The school bus in my game for all my families that I play with does not show up to take the kids to school in the morning. The bus will drop them off back home after school but won't pick them up. I've uninstalled my game and reinstalled all games in the order in which them came out. The only mod I have is to skip the intro video when the game is started. I have researched this problem and have not found a solution.
I've had that also, If they do not goto school by them self you can always send them there manually by clicking on the little arrow on the career tab, if it's children get them a bike, if teens get them a car and teach them howto drive if you have the expansion that require that, and they'll use that to go there instead of getting a cab.
Annoying to have to do so, yes but only "fix" i can think of.