I would contact whoever is in charge of the school and let them know what happened, so that they can be aware that there "may" be a problem with their transport system. I would not care that it is the first day for the driver or not! It should not happen! One can still also say something 'nice' about the same driver to the principal!
You can compare this to giving a patient #10 the medicine of patient #1, just because the nurse started at the 'wrong end' of the room with giving the medicine. No excuse - she needs to realise just how BAD it could have turned out - she will guaranteed never do it again.....hehe..... (been there, done that once a very long time ago

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Kids are precious - a negligent driver is NOT acceptable! Think of future kids he/she transports.
Now I will get off my soap-box......