Son with SEN unhappy at school

[Itwontrainallthetime]

I apologise if this is a bit long it's quite complicated.
My son was assessed in the infant school he was at and it said in his reports he has significant learning difficulties. The infant school was brilliant and had lots of ways they can help him and he improved. However he went into junior school he was in a class 3/4 and the other class was just year 3.
He struggled and it seemed they had no plan in place for him so i been in etc and we got someone else to come and assess my son and she told the school what he needed to improve etc and the teachers and teaching staff have been brilliant and he showed improvement.
Last year my son was in just the year 4 class so not with the year 3s mixed etc we saw a massive difference and he had come on massively and was really improving and they said because what they were doing is working they will keep everything in place going into year 5.
Before they broke up for half term I was wondering which class he would be in just the year 5 or the year 5/6 mixed again. I was hoping he would be kept in the single year 5 class as he improved massively and didn't want him to be set back again as I know he didn't really like the 3/4 class he was in. I thought that they know his needs and everything will be fine. But it really isn't and after having a meeting with his teacher before the half term just gone she had told me he is struggling again and is even further behind. For the past few weeks of term my son hasn't been himself he's been coming home with a full packed lunch and says he can't concentrate in the lessons all the children just mess about. And that he hasn't got his visual time table so doesn't know what's happening during the day. He told me this last week.
I had a meeting with his teacher a few days before they broke up for half term and I said to her that I was worried about this happening if he was put into a mixed class again. His teacher just pulled a face and said she didn't think it was because of that.
I'm sure it is and I don't know why they do the mixed classes. Is it to do with age, as if it is then why wasn't he in the mixed class last year or is it because of abilities.
Would it be worth him moving back into the class he was in last year as there the same people in that class they don't tend to me moved from class to class.
I know my son has SN but he likes structure and most of the kids in his class do misbehave and are loud as they have complex needs too. But my son tends to need the ones that appear to be say more able in order to succeed.
I'm at a loss and don't know what to do now.

I think you have a good grasp of your son's needs. What you are describing reminds me of the 'relaxed performances' that cinemas and theatres can offer - allowing children and young people to attend who wouldn't normally, because they shout out or get up and cause a disturbance. I totally approve of these, but they don't work for my son, because he needs quiet and calm, so we would avoid these performances.
I think each teacher in the school will have a different level of understanding and what will work one year with one teacher might not work the next.
My son was moved up and down year groups so he would be with the best fit socially (in a special school). If you think you have identified a group that fits well with your son, then I would be pushing for that - 'reasonable adjustments ' is the key phrase. Do you have an EHC Plan, because if not, I would contact IPSEA/SOSSEN and consider starting the process of obtaining one, because when he moves to secondary level, he probably will need one and depending on the level of his learning difficulty, might benefit from attending a school with a resource base/SEN unit.
Best of luck.