It is such a RELIEF to read your posts!!
I too have a DS3 who is in prek for the first time, his teacher shared that he needs constant redirection and isn't following directions. Stayed after to talk with her, and my LO is playing easily with her 5 yo son, and consistently following my 3-4 step commands. She was amazed at how different he was.
To me, I think my son is just overstimulated at school- new setting, 7 kids in class, new toys, new routine, busy place. Compared to our quiet home, play with me/adult, only child...etc. It is just a lot to take in.
That being said, my child is never still, seems psychomotor OE for sure, and is a joy to see in movement- physically very coordinated.
Hopefully he'll continue to improve his ability to sit, listen, and filter out the external stimuli that seem to be making it hard for him to attend/answer.