Mine & my son's experience of school gym swim lessons was that by the time you travelled to the pool and got changed there was so little time to swim it was hardly worth it. I left school barely able to swim (since self taught) and we paid for private lessons for son, which were much better quality and ratio than those a school PT instructor could give.

That said swim lessons within the school curriculum reach children who are disadvantaged and may otherwise never get to a pool. For that alone they have worth.

The guy in the video has seriously lost it, perhaps he is having a breakdown, maybe he has a lot of stress he can't cope with, either way he shouldn't be teaching.