dunravin, I had the most horrendous time sitting by the poolside, trying to keep my (then) 3 year old son out of the pool while my oldest son had his swimming lessons. At times I would witness my 9 year old mucking around in the water and not listening to his teacher, while my 3 year old was intent on trying to struggle off my lap, run round the edge of the pool, throw toys into the water, while shouting gleefully at his older brother. I dread to think what all the other parents thought of us. I seemed to spend my whole time being cross with one son or the other. And things got even worse afterwards, when all three of us would be in the changing room. My oldest son procrastinated so much!! Many was the time I was close to tears.
In the end I was allowed to take my youngest son to the playpark next door to the pool, keeping my mobile on in case I was needed. My oldest son was better behaved in the lessons and got dressed more quickly if his brother was out of the way. I checked this with the teacher and we agreed things were working much better. I used to wait in the reception area for ds1 to arrive dressed.
However, one day a temporary teacher took the class and when I came to collect my son she was incandescent with rage. She told me off severely for leaving my son alone, was unprofessionally nasty about my son and told me he had been wildly swinging off equipment in the changing room (something he had never done with me). When I told her about the arrangement I had with the regular teacher and suggested there had been a breakdown in communication her end, she just got angrier and implied I was lieing.
Later on I checked her version with some parents and the caretaker who was present when she ranted at me, and they all said my son had been ok in the pool and changing room and her version was very exaggerated. I took this up with the swimming school. The regular teacher who ran the school said the temp teacher was a friend of hers. Gave no apology for the teacher losing her rag with me. I was asked to sit in on future lessons - fair enough, but I had only ever left because I had been allowed to. Still makes me cross thinking about it.
Sorry, rambling here, but just wanted to say that swimming teachers IME aren't always right. Their teaching conduct is not closely regulated by any central body, as I found out, so they can do what they like. I looked into making an official complaint, but the regular teacher told me there was no one to complain to apart from her! and basically she was right.
Hope your son's next swimming lesson goes smoothly.