Since this is his first offense, he would most likely be offered a deferred contract which states that he promises to complete a certain number of classes, community service and have no further contact with the move theatre for 6 months (maybe a letter of apology to the store manager) and if he successfully fulfills the terms, then his case will get dismissed. You should consult with a Juvenile Defense Attorney in your area.
This answer is for advice only. No attorney-client relationship has been established.
He is a juvenile. Having never before been in trouble, he will likely be offered a deferred which is like being on probation. He reports for 6 months and does a few other conditions and then the case is over and no one can access juvenile records except law enforcement (and he can seal his record when he is 18 if he gets in no additional trouble.) OR, they might just make him write a letter of apology and scare the heck out of him and let the case go.
His worst-case scenario is likely a short deferred probation with requirements like an anti-theft class and community service hours. Deferred is the kind of probation that does not result in a conviction. I would hire an attorney in your area that regularly handles juvenile cases. He will be able to get you the best result.
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