Sons voice changing but teacher refuses to move to different voice group

So long story short my son is going through puberty which means his voice is changing. The teacher has him singing alto even though he has told her that it hurts trying to stay up in the higher ranges. The teacher however refuses to try to move him to a different range because he will have to relearn everything according to her. Is this a normal reaction, argument from a choir teacher? I don’t remember this being the case when I was in school, but maybe things have changed in the last 30 years.