Other mistake: During the police chase, Mick hits Paco's little brother and then slams into the white van, and it instantly bursts into flames creating an inferno. Which would not occur under normal circumstances. But merely dramatized for movie effect.
Audio problem: When Horowitz is being taken to Solitary, his lips do not match what he's yelling.
Factual error: I don't know of any court system in the U.S. that will allow a person, teenager or not, to get into shootouts, steal a car, and maliciously run over/kill someone while fleeing a crime, and all they get is time in a juvenile detention center because they're underage. Whether you're a teen or not, if you commit crimes like that, you get tried as an adult, no exceptions, which means prison.
Revealing mistake: After Mick and Paco fight near the end, there is no blood on either dude just before Mick pins him. And then suddenly both their faces are covered in blood just before Mick stabs him with the knife.