This is an interesting question about Edward Bloor's novel Tangerine, and it does not have a direct answer from the text. Readers must make inferences to determine the answers to why Joey acts the way he does at Tangerine Middle School.
The circumstances surrounding Paul's transfer to Tangerine Middle School were quite different than Joey's. Both boys had the option to transfer after the sinkhole at Lake Windsor Middle School. Paul jumped at the chance to transfer. He had no hope of being on the soccer team at Lake Windsor because of his IEP. He felt his mother ruined his life with his IEP, and transferring to Tangerine Middle was a fresh start for him. Paul was new to Florida anyway, he would have been new in any school, but that was not the case with Joey.
Joey was dealing with the tragic loss of his older brother, and that caused him to change in ways that could never be predicted. His only reason for transferring to Tangerine was because Paul asked him to, and they had become fast friends. Joey was on the soccer team at Lake Windsor, though he was not getting much playing time. His father got special permission for him to play at Tangerine after tryouts, and the other players are probably aware of this and resent him for it. Tino begins making fun of Joey for sticking so close to Paul all the time. He calls him "Charlie the Tuna" and insinuates that he has a crush on Paul. Paul is able to ignore these insults, but Joey, in his raw emotional state, is not.
Paul also reveals something on the entry dated October 3rd that insinuates that Joey could be racist or that he at least looks down on students at Tangerine Middle School for their lower socioeconomic status. Here is the exchange between Joey and Paul:
I said, "Where's Theresa?"
"Theresa Cruz. I told you to ask for her as a guide."
"Oh yeah. She's back at the office. I saw her there."
"What? Is she guiding someone else today?"
"Nah. I just didn't need it. What do I need a guide dog for?"
"A guide dog? You're calling Theresa a guide dog?"
Joey laughed. "C'mon man, lighten up. What? Do you think she's good looking?"
I thought about that. "Yeah. I guess I do."
Joey still had that cocky smile plastered on his face. "Then you've been here too long."
I couldn't believe what I was hearing. I just shook my head. I finally said, "I gotta tell you, you're coming in here with the wrong attitude."