Uhh no. Leaving kids stranded at a bus stop is a huge liability for the school because if the kid wanders off and gets hurt or gets in trouble, the school could be held at fault. If a bus company is leaving kids stranded more than once in a blue moon, they will lose their contract.
Nah, the school can blame the bus company, and the bus company can blame the school. Any queries about abandoned children just get bounced back and forth until the matter is forgotten about. Split liability typically means no liability.