Can you tell when a student is the only child or oldest?

My 3.5 will start PreSchool this Aug (Mon-Fri 12-3pm). He will be 4 in Sept and never left my sight. Like never ever. Lol

I tried taking him to PreSchool last year but I wasn’t ready lol. Teacher said he cried and asked for Momma the whole 3 hours and I finally took him out when he would just cry himself to sleep there…and he wasn’t even going around nap time…

Back to my question on top.

Can you tell when they are the only child? Like not used to sharing? Or communicating with other kids?

I tell him now about school and he still says he wants to stay home with me

Any advice