I think he's being picked on a bit because of his wee bit eccentricity
I would go to see the teacher again or even better the head teacher and voice your concerns and nip it in the bud.
We have been in to see our headteacher today as there have been some worrying goings on involving our DS with similar toilet door busting antics and egging him on to do stuff that he doesn't want to do. I feel so much better for having the chat with the head and knowing that our concerns have been taken seriously.
Our school also has a buddy system in place where the younger kids are buddied up with year 6 kid who they can go to for support if they are being unfairly treated and they have a bus stop bench where they can sit if there is no-one to play with and someone will come along.
but, on the other hand, DS has equally said no-one plays with him, but he has just meant that playtime, but to hear his rendition of it, it's all the time. We have asked at school though and he is always running around with someone. If he has had a bad day, it tends to colour his entire viewpoint of school.
I know only to well how difficult it is to hear your child say that my DD1 is just 6 and also in YR1 and has AS, and she rarely plays with anyone at school. It breaks my heart , however on the whole she is more than happy to play soilitary.
Just my opinion oops, but i think that the fact that he is now in a new classroom, a new teacher, new TA and probably a new classroom routine is probably at this point enough for him to take on board, afterall is takes most children at least a half a term to adjust, so at this point i wouldnt worry about him not playing with the other DCs while ever he is happy.
Sorry ive just spotted the time and i need to pick DD2 up from pre school.....i will be back!!
IKWYM about seeing the teacher all the time, i always feel them same, however i think you have valid reasons to tbh.
As regards these 2 girls, i does seem like they are taking advantage of your DS passive nature, some girls at this age can be really mean at times. DD wont even bother with the girls tbh....they are far to complexed LOL .
I think your doing the right thing, in nipping it in the bud early doors.