I try to look at what my kids want and need, and not to project my own wants and needs onto them. If your DS is happy being with just you all day, and doesnt' actually crave peer socialization, then he might NOT be benefitting from that aspect of school. He might simply not be ready to be away from you all day.
Being in school and around other kids is NOT a guarantee of making friends. I can think of several years of school when I literally had one or two friends, and neither of them went to my school. This happened in 3rd, 4th, 7th, and 8th grades. In 1st and 2nd, and again in 5th and 6th I was in special ed and had friends in the classroom. I think I had more friends in kindergarten because I hadn't yet alienated my friends from preschool, but I didn't make a single friend in school. By high school I was ready and I had a good social life.
DS started out 2nd grade with friends in school, but by the time the school year ended, he didn't consider any of them his friends anymore due to bullying and teasing. I'm not convinced DS was only the victim with the bullying- it seems he bullied back as well. My sweet, sensitive little boy turned into a rude, violent bully.
He's getting better, being home with me, but he's still not fully healed from his school experience.
As for the whole "start school in jr high vs starting in high school"- it does sound logical. High school was when I was finally ready to be in a school environment (after 9 years of being miserable in public schools) and I figured it would be the same for DD2, if she chose to go to school at all. But then she wanted to go for 8th grade. Overall, I do think it's working out better than if she'd waited another year. She's got a full year to "learn how to learn in a school environment" before she's in high school. Most of her classes won't count on her high school transcript. The only two that will (Algebra and Earth Science- 8th grade honors doing 9th grade work) she has the option of dropping out of (into 8th grade regular) if she's really struggling.
Overall, she's doing fairly well and she's DEFINITELY happy there. But it's still stressful and she can be so dramatic when she's having trouble with homework. I'm looking forward to the time when DD2 can do her homework independently, with only the occasional question (say, a math topic she's confused about) instead of me having to sit with her and "teach her how to learn" with almost all of her homework.