I remember your other thread. You need to phone and ask to speak to head. If she/he is out, say you have an issue with a child safety, and would like to make an appointment to speak to her today.
Write down the incidents. This is VERY IMPORTANT. You need paper trail to prove you are not just moaning. Make a list of dates and inciidents your ds has told you about. Include the times you have spoken to the teacher.
When you see the head, take the approach that you don't want to criticise the other little boy, he is just a kid, BUT your ds is not safe in that class. He is being hurt on a regular basis. You have tried nicely to leave it up to the teacher. This has failed. You now expect the school to take action.
Be very clear. It is up to the school to protect your child. It is not your problem how they do it, or what happens to the other boy, but the school has a safeguarding issue here around your child.
Sorry just seen your last post. Yes you are doing all the right things. Remember that you need to be nice but firm I say that because as soon as you get angry etc they stop listening. be like a broken record. My child is not safe, it is your responsibility to ensure he is safe.
Keep copies of your log, and give school copies. If the head doesn't help, send copies to chair of governors and ask them to take it up with the head.
I know of a couple of kids with sn who can be aggressive in school. Both have 1;1 TA. One of them the TA was asked to do something else and so was not alongside the child. he then bit another child. The parent (of SN child) pointed out that he had a 1;1 for exactly that reason, he was fine a lot of the time, but when he wasn't he needed an adult there close by. The TA has never been called away since!