I should have mentioned they did not teach any of the kids that were swimming in the same group with my kid.
I'm really trying to understand here: what were your expectations?
Your kid started out in a beginner swim class. What skills were you expecting the kid to master, and how quickly?
Has the kid learned how to blow bubbles? That's a skill.
Has the kid learned how to float on his back? That's a VERY important skill.
Has the kid learned how to put his face in the water? That's a skill.
Has the kid learned how to use a kickboard and kick his way around the pool? That's a skill.
Were you expecting him to swim laps and join a swim team? That requires not only swimming skills but endurance.
I will also add that until a child is developmentally ready to swim, they simply will not swim.
I know for myself, that in spite of swim classes as a preschooler, I did not swim until one day, I was watching my mother do laps, and decided that I could do that, and just did it. Prior to that moment, I did not so much as do the dog paddle. I was 5-6 years old.
I observed the same thing while teaching swim lessons. Most children simply could not focus on anything but play until around 5-6, and as a result didn't learn much in the way of proper swimming until then.
I strongly suspect that your child learned something about water in those lessons. I would be more concerned if you said that the kid was terrified of the water and they just continued tossing the kid in, or shoving the kids head underwater.
But either way, the kid took the lessons, the instructor's time is worth something.
P.S. If you try taking the swim school to court and display half the attitude that you have here. with the same amount of "facts", you should count on not just losing, but having any non-absurd counterclaim granted.