How, if i understood your post, that's a bad thing indeed. I know firsthand how a school day can be hellish when others suddenly decide to pick on you... Hopefully it's just the first day indeed and that things will get better. I guess a good thing is to not let yourself get step on the toe and to not be too shy,

They didn't pick on, they didn't talk to me at all.
So I don't have to worry about let myself get step on.
Now being shy... I don't know.

The bigest probleme is what they know about me :
I'm Pierre and I'm an autistc.
That, thanks to my first teacher.

Thanksfully they seems... cool.

Well, i'm one(well, a light one), and that doesn't cause me any problem in public. So, as long as you don't do 'strange stuff' on purpose(and you definitely doesn't sounds like someone that would do that), it will be fine.

By experience, the best way to fit in is to be...less shy, without overdoing it too. You can stay yourself, but if they start to pick on you, just don't let that from talking/being social with those that don't. Their opinion of you will be based on how you act, not on how that teacher described you!

Hoping everything will go well for you tomorrow, but from what you describe i don't think you have too much to worry about!

Hey.
You know what ?
When I actualy get to the doing, the section I'm in get actualy really cool.
And everyone in cool too.

If I could talk to my past/futurself, it would go like...

PMS : PIERRE !!!
FMS : ...
FMS : WHAT !?
PMS : Stuff sucks a lot today.
FMS : Okay, shhhsh
PMS : Huh ?
FMS : I know things are tough now.
FMS : But trust me, things will get better.
FMS : Cuz' I LIVED THAT SHIT !

Futur me is always better me then me and past me.
Always.

Cool! Glad to hear things did get better!

My future self would probably be a teasing jerk toward my past self, gloating about how he have access to time travel and not i!