Secondary school advice needed

Hello everyone!

My son is in year 5 now and we will have to apply for secondary school places this October.  He has high functioning autism and is academically able.  However, he has severe anxiety and maybe PDA (not diagnosed) and he finds the social interactions in school very stressful. He has various sensory issues and struggles with certain noises, odours and tastes. He masks well at school but comes home and behaves very badly; lashes out at us in anger, avoids self care and doesn't want to do homework. But he is very creative, humorous, a voracious reader and generally intelligent.  He doesn't have an EHCP because the school feels he's very able, well behaved and there is no evidence of an issue.

My son's inability to cope in a social environment, makes him awkward and very prone to bullying. Also he finds it hard to deal with strict teachers and feels terribly anxious about being shouted at.

Given his ability, he needs to be in an academic environment is what I feel.  He could well get into a grammar school, if he prepared well.  He is a good learner and deserves to go to university.

Many friends have advised me that he needs to go to a private school with a small class size. Given his talent I don't want him to be deprived of a high quality education, but at the same time I want him to be in  a school where they understand his condition and provide appropriate support.  His current state school simply cannot understand his issues.

The NAS has listed a few schools with a specialist unit. If your child attends any of these schools especially Salesian in Chertsey, Surrey, please can you let me know your experience.

Also any advice on either private or state schools would be highly appreciated. I am ready to move if we find the right school. Right now based in greater london borough - east of london, but can move to surrey and nearby areas.

Thanks so much!