Hi, my son started when he was 4. Far too young for him and he found it hard to settle but he was my first born and I stupidly believed the lying headmistress who told me that if he didn't start then he would lose his place and could end up in a school miles away!
He is an adult now!
My own view is that school isn't just about learning, the social interaction with his peers is very important.
My son was 4 at the beginning of August and started school in the December, mornings only then full time in the January. I came up every day to hear how he was swinging his book bag, fidgeting in class, running around, getting up out of his chair and it was very difficult for a time. He was always the youngest in his year with some children in his class nearly a year older.
My biggest regret was not keeping him back a year and saying to the school that he should have been in the year below. A girl round the corner was less than two weeks younger than him and was in the year below.
You could meet with the head and discuss your concerns. I don't know if now he has started that it would be wise to take him out of school and hold him back a year or even if you are allowed to do so. It could make him think he has done something wring when all it is that some children, especially boys are still very immature at 4 and are simply too young to settle in school. Some children are ready at an earlier age but my own findings when helping out in the classroom once or twice a week to do crafts was that the girls in his class were very eager to please teacher and had sitting down skills much better than the boys and there were a few boys who to me seemed too young to be in school.
I sympathise, but truly believe that home schooling is not the answer. Star charts and rewards for good behaviour are tiresome as you think your so will never settle in school but eventually they do grow up and he will get there!
My own view is that in the UK many children start school at too young an age.
Just keep going up the school and talking to teachers and headmistress.
I was annoyed that in one class the teacher gave lollipops to six boys who were deemed the restless ones causing distractions in class as an incentive to behave.
I complained and said what about all the well behaved children who turn up every day and do as they are told? Shouldn't they deserve a treat!
If you can spare time, volunteer to help in class, then you may be hands on with your son and he may settle better knowing you will tell him off in front of his class if he doesn't!