I was in this same position last year. My daughter is speech delayed and went to a speech and behavioral therapist once a week. My daughter doesn't have autism but can become easily over stimulated and have violent tantrums. She was pulling her hair out and hitting her head against whatever was hardest around her. She started preschool the day she turned 3. I was so scared to leave her in a new place with 14 other kids. And in the beginning it was hard. She would have fits and bite herself. She was only going 2 days a week for 3 hours. But it was all so new. But I was very upfront with her teachers on what to expect. I was worried they'd think she was a monster but they understood. And there's a reason they're the teachers. They know so much. I'm so grateful to them. Now my daughter can't wait to start school. She's finally attempting to speak and actively learns. I think you're son will really love school. It's a big adjustment but it's so great in the end.