Is this a true story? My son has autism (profound/severe) but I also am on the spectrum/Asperger's (although they aren't really using that term anymore, I understand.
And so I can relate -- to the feeling of panic when everyone's looking at you and using my long hair as a curtain drawn against the world.
A few suggestions: when you have internal dialogue (the repeated swear word in the beginning, for instance, try using italics. That way the reader is put right into the mind of the narrator.
There are a few places where you could shape up the sentences with better grammar - for instance, here is one edit. Your original paragraph:
"So we have a new student with us today," The teacher started,my face went bright red, "Lillian, would you please come to the front of the room and tell the class something about yourself?"
My edit to that paragraph:
"So we have a new student with us today," the teacher started. My face went bright red. "Lillian, would you please come to the front of the room and tell the class something about yourself?"
And here, you want the word "too" -- Oops, maybe that was to loud.
I like this part a lot:
I fell. On my face. Painfully.
The sharp small sentences mimic the fall, and it's effective. And here, you do it again:
This. Is. To. Much.
However, as before, you want to use "too," not "to."
Toward the end, "highway" is one word, and you need an apostrophe in "Im."
I might suggest adding more to this - about what happened after you got home, about how your brother acted toward you - or your parents - or the kids at school the next day. You draw your reader in nicely but then leave us hanging, wanting more. And that's a good thing!
Thank you for sharing.