We tried it with ds1. We had a statement specifying 100% 1:1. I wouldn't have let him go to school without it (although they tried to get away with 0.8).
He sounded like your little boy at the time tbh. We had a lot of problems. How does your son communicate? DS1 used PECS, there was no-one in the school PECS trained. They had no idea how to react to him and he quickly went from the very passive, sweet little boy he was in nursery to having a whole host of challenging behaviours that I knew nothing about (until his private SALT wtinessed them and had a quiet with me- she said the school were escalating the siituations and I needed to act quickly. The problem was a complete lack of understanding about autism. After 4 terms he moved to a wonderful special school and has just flown, the quality of teaching doesn't compare.
In your situation I'd ask to see all potential schools (we were fobbed off and told we weren;t allowed to see special schools when ds1 was 4- absolute rubbish I know now). When you go round, ahve a look for children like your son, see how well they are integrated in the classroom, do they look happy? Are the learning the sorts of things you would like your son to learn.
At mainstream ds1 had an adult with him all the time. He was completely isolated within the school. He spent most of the time walking round the school, occasionally standing (alone with a helper) in the playground watching cars go past. I don't think he learned a single thing in his time there.
We went to look at special schools, in one children like him were kind of cordoned off, bloackaded into a corner of the room, we knew it was the wrong place for him.In the other, we arrived just as his calss was setting off for a trip out, The children were waiting nicely, the teacher had a clear system to encourage good waiting behaviour, there were visual timetables, the children looked safe. we chose that one and it's been great. He's actually far more includede now thatn he was at mainstream.
Which isnt to say that mainstream can't work, but I do believe if you have a child with very limitedf speech and language in particular it is a big struggle to get it to work. A child with limited speech and language will have very different educational needs from the rest of the class. You need to ask how they intend to include your son, how much training staff have (one day isn't enough), will they pay for proper PECS/Makaton training- impossible for an LSA without that. HOw many LSA's will they employ. What happens when the LSA is off sick (you getting asked to keep your son at home for the day- that used to happen to us- is completely unacceptable). Who will make the necessary recources, who will provide PECS books (when ds1 was in mainstream the answer to that was ME- now in special school they send me stuff home to help us out).