Thanks for the response.
In Washington State this is a fairly serious charge. Theft with intent to sell items valued between $250-$1,500 is a Class C felony. If the items were worth over $1,500, it's a Class B felony. Here's the statute for you to see what the charge is all about and what the state would have to be able to prove. (see link)
On the Class C felony, there would be a minimum of 18 months in jail and a maximum of five years of prison. On the B, there would be a minimum of 3 years in prison for this offense and a maximum of 10.
I don't want to scare you to death, and I don't see your son as having to really worry about jail here. However, I did want to tell you what the charges are worh on paper.
He needs a lawyer badly. If you can afford to hire one for him by his court date, have the lawyer with him when he goes to court. If neither he nor you can afford counsel, he must go in on his court date and plead not guilty and then ask the judge for a public defender. The judge will assign one if they believe he is financially eligible for one, which is to say poor. Different jurisdictions decide what "poor" means to them differently, but the important thing if he doesn't have a lawyer on his first date is that he has to plead not guilty.
Even if he wants a plea down the road, the only plea that keeps his rights open so that a lawyer can negotiate something for him is a not guilty plea.
Long term, the fact that he owned up to this to the school, that he's already paid back the school, taken a course and attended counseling is great news. It shows he understand accountability and he's looking to get his life back under control.
Characteristically, a prosecutor will reduce the charges and offer a deal. With luck, particularly if the school is content with the remorse he's shown, the prosecutor can drop the charge to just a regular theft offense. With that, he can get probation, and there are even special forms of probation that could allow someone to complete the program of supervision successfully and then get his charges dismissed.
Presently, his charges are too serious for the special forms of probation. But if the school and the prosecutor aren't hell-bent on destroying his future, and given the steps he's taken to help himself, a lawyer may be able to negotiate something very favorable for him. Otherwise, I'm confident he'll be offered straight probation and will at least be able to avoid an incarceratory sentence.