we didn't repeat prek, but did repeat K, and it was the best thing for DS. Though fe doesn't have a dx of autism, he does developmental delay, a speech impairment, some ocd, and very ADHD. At the end of last year, he couldn't recognize sight words, or write his name, wasn't socializing with any of the other kids, etc. Although the principal at the school insisted on sending him to 1st with an aide, thankfully we were transferred to a new school right around the corner from our house. They, and a teacher who knew him from the other school, really heard our concerns and supported our choice to repeat. Now, at the end of that year, he's reading halfway through first grade level, and is on grade level in his writing, and interacting better w/ peers. He does get 2 hours/ wk of inclusion support for social skills, and OT and speech. But now, for the first time in his life, he verbalizes that he's "smart". He wants to read, he is doing 3rd grade math (and beyond), he's a much more confident kid. If we had put him into first grade before he was ready, I really believe that we would have required much higher levels of support for him, and potentially damaged his confidence and ability to succeed academically and form relationships w/ peers.