What is so wrong about appearing to be precious about your son?
For most parents, our children are the most important thing in the world to us.
This thread brought back memories of English for me, which I guess are similar.
I was in year 10 (not called that at the time).
Weirdly those in the top two maths sets got to do English language and English literature, so since I was in the top maths set I had to do eng lit as well. I didn't want to and wouldn't have chosen to. If it had been based on English ability instead of maths I wouldn't have been picked to. I'm dyslexic and didn't enjoy English tbh.
Then I realised I had the English teacher from h ell. She obviously modelled herself on one of the three witches of eastwick. She realised quite early on that I struggled with reading out loud. Consequence, she made me read out loud in EVERY lesson. Try reading Shakespeare when you haven't read it through beforehand when reading isn't your strong point.
At first, I thought I was imagining it, so I kept a record of who she made read in every class. I wasn't imagining it. It was just me.
At the end of year 10, she had a one to one discussion with everyone about their progress and I, along with a few others, were told that since we were struggling with the lit side we could drop it if we wanted. I said yes in a shot, basically as I thought I would get moved out of her class. Unfortunately I wasn't but it put a stop to the reading issue.
A few months into year 11, she was going through exam entries and it was apparent she had entered me for Eng Lit after all. She told me it was too late to withdraw me and I would have to do it. Of course she then told me I would have to work hard to catch up. From somewhere I found my voice and told her that wasn't going to happen. It had been borderline whether I would pass as it was before I dropped it, and I wasn't going to jeopardise my other subjects by trying to catch up for a subject I didn't want to do and I wasn't going to do any work for it. I took the exam as required and got a U. However I did get a B in English Language, which I'm proud of.
A few years later my sister was in a similar position. She knew she would get this same teacher for English, so got my mum to write a note saying she didn't want my sister doing Eng Lit. With hindsight, I wish I had got my mum to do something. However I was a few years older than your son now and probably better at dealing with it myself as a result.
This seems like bullying behaviour by this teacher. Ask yourself if you would tolerate similar behaviour towards your son from one of his peers.
As others have said, talk to the teacher first, then if there's no joy, move on to HOY, etc. This teacher needs to know the effect he is having on students, if he cares he will do something about it. If he doesn't care, he needs to be dealt with.