My brother 15 years old was accused of attemped arson but never set anything on fire how long can he get in detinton?

What he could get depends on the current charges, whether he is guilty of the charges or not and any prior record. A good criminal defense attorney can help sort this out for your brother.

I agree with George. There is not enough information to help you but find a lawyer and let them ask the right questions to give you the right answers. Most lawyers provide free consultation anyway.

It is impossible to say how much time your brother might receive for his actions - if they can be proven. The factors the court will look at are his past record (if any) and his overall character. The court could also give him suspended time so that he would have to enter detention if he commits other bad acts during his probationary period.