@Corilee2806 I was almost exactly in this position last year. DS always struggled with going into nursery, we tried EVERYTHING. I was in tears thinking how I'd manage getting him to school 5 days a week (he also did 3 days at nursery) He should be getting his autism assessment this summer after being on the pathway since 2.5.
On a 30 mins STAY AND PLAY at the school (so I wasn't even dropping him off) he was the child trying to run off, crying his eyes out... When they bought the sign in sheet out he genuinely screamed "DO NOT SIGN ME IN... I'M NOT GOING IN THAT PLACE" It was meant to just be one parent person child but they let my mum come too as it took both of us to get him in the door.
It's a bit different as his nursery were incredibly supportive and got the school on board when they forwarded on his info. His school teacher visited the nursery and we had meetings to set up some things early on - DS was allowed to take his comfort rabbit in, wear his cap in school, we'd get there early so he was one of the first ones inside. They spoke to nursery about his routine and set it up so he could go straight to a set task to help him regulate. Some of his friends from nursery are in his class which was a massive help.
At home we got books about school, tried his uniform on a few times to make sure it was comfy (he doesn't wear the branded stuff, he finds the Asda stuff most comfortable), practised the walk to school. I'd tell him stories about when I was at school. I was also really empathetic with him and said I was nervous starting school and got upset some days, but I'd loved learning and made friends etc. That especially really helped I found. He has ear defenders for the lunch room if he needs them and they have a "quiet room" he uses some mornings.
He started in September and honestly, he is THRIVING!
He loves the routine and structure. Loves learning. Has some lovely friends.
He gets overwhelmed and needs support, some mornings are still very hard and he needs some weekends to just "re set" but he's always very positive about school itself. He's on their Sen register with an ilp (individual learning plan) We have regular meetings and they are all for helping him thrive.
Most mornings he actually walks down happily chatting and goes in after a quick hug with no upset at all. If you'd told me this a few months ago I wouldn't have believed it.
He's on accelerated progress for the academic side and has gained loads of confidence.
My advice would be communication with the school and following his lead a bit at home. Send them any paperwork you have to support your concerns/confirm he's awaiting assessment etc.
Keep a morning routine so he has time to things without rushing. Take snacks to pick up and don't ask many questions straight away. Play "school" and "office" as a fun way of practising some of the stuff they do, it might help him open up about how he's finding it too.
I also really worried about not much transition - he started on a Wednesday full days and the next week was full time. But I actually think it helped. The repetition and structure set the routine up quickly. If he's had ages of transitions he wouldn't have known if he was coming or going thinking back on it.
Good luck op!