Hi Blue Metro.
Hope the summer hols are going well. I am not an expert in this field, however, our son has sensory issues, so I can share a few thoughts with you. Has your son had the Sensory Tests via the NHS? I am guessing perhaps not, as the diagnosis gives you support in terms of clothing and coping with all things sensory. The test can be accessed via your social worker.
With regard to day to day life in secondary school, again I am no expert, but happy to share our experiences. Our daughter has just finished year 7 and our son starts year 7 in September. It sounds like you are acing things, but these suggestions may help:
Build strong relationships with you sons key teachers e.g. year6/7 transition lead. SEND/inclusion lead. House/year 7 pastoral care lead etc
Ensure your son has key teachers he can go to when things can difficult (our daughter has 3!)
Has your son a "pass" that allows him to leave each lesson 5 mins early to avoid the crush when the bell goes at the end of each lesson?
Can your son manage a full day? Set up with the school that he has one rest period (every day if necessary).
Does your son have access to all the school inclusion type things that they have on offer? E.g. Forest School, any therapeutic support/mentoring the school provides etc.
What and where will your son go at lunchtime? Unstructured periods can be tough for our children. Is there a break time inclusion/quiet room supervised by a qualified teacher that he can go to?
If things get really difficult over the holidays e.g. your son becomes really anxious. Get in touch with his lead secondary transitions teacher and let him/her know (yes even in the holidays, that is their role in the school!) This will at least give you some peace of mind and give the school a heads up, before the start of term.
Hope some of the above helps. Very good luck to your son.
Take care
Simon