I did it with ds.
He is summer born, and just wasn't ready for preschool. He stayed at home, we had a nanny 3 days a week, he got loads of experience and preparation.
He does have ASD, very high functioning, and he would not have coped with the social side at all when younger.
Having that extra year at home meant we (his nanny and I) could do a lot of groundwork on the social side at a pace he could cope with.
He didn't really go to groups, but did have a lot of outings. Whenever there was a social side, he got full 1:1 support, which he needed at that time.
He started reception last September, and has been absolutely fine. A bit quiet and shy for the first term, but nothing extreme for a very young 4 year old starting school.
He is at an independent school, so only 18 in the class (with full time TA plus teacher) which does also help.