"Here was my favorite teacher, in front of the class telling me I couldn't handle it."
Speech: Thanks a lot sir, for reminding me!!!
Oh confound it all! What I'm trying to say is that you're not normal -
From this I can infer that Percy cared a lot about this school. He feels as if his teacher saying that he isn't worthy of being there.
I can infer from this that Percy felt so offended. Because he misinterpreted his teacher saying that he's different because he is special, from him saying that Percy is different because he's a dyslexic kid.
Action : But I was already gone... (I ran out of the room )
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From this thought I can infer that Percy cares a lot about Grover. HE is worrying about Grover so much he is losing sleep.
"I'd lost sleep worrying that he'd (Grover) get beaten up"