1st NAH! , coach Hill from the start knew what Mc was doing , that is why coach H. took Nadia and Zara to the locker rooms to explain to them what have just happens and gave 'em the handcuffs to get revenge on Mc for making them look like fools.
that's why Coach H. goes back to the locker room to talk to the other class and she gets shock to see Mc still there.
2nd NAH! , when you're a teenager (till 16 or 18 depending the country) your name and mugshot can not be made public by law and once you've been sentence or exonerate your casefile is sealed , so your name or mugshot will never be on police computers or records either .
unless the crime you did was really awful , they will make an exception to judge you like an adult .
1 Yeah, it COULD be that simple, but considering that Hill has been watching Nika for year before, from before Summer was gone, and even after, and knowing Ocean loves plot twists, the simple neat answer might not be the case. Coach Hill would be risking her job if it got out she helped students handcuff a guy in the girls lockers - she would probably be worried about her job because Nika ripped Zara's top, and Hill didn't do anything official. Gotta get that plausible deniability in place to keep a university job safe.
2 Who said anything about public? The police database isn't public. Where I live, serious offenses (such as involving violence, most likely what Nika's been charged with) stay on record. Even in the case of the charge becoming spent, it will show up in some background checks for employment. It really depends on what the laws are where you live.