From the trailer, a film by Ina Weisse - Das Vorspiel- here: https://slippedisc.com/2022/04/how-merciless-is-your-violin-teacher/ I have seen more than a few teachers like this.... Art imitating life? I would guess this behavior doesn't fly now, but we keep hearing stories on Mnet of "mercilesss" teachers (and worse)...
Nevertheless, the trailer looks interesting. How many times did I miss the bus or carpool as a youth? A perfectly reasonable excuse, imho.