not finishing a dui school course.

People miss classes for DUI and other court ordered classes all the time.  The courts are very reasonable about excusing a missed deadline or failure to pay a fine.  Basically if the school reports your absence, you must get reinstated and go to the courthouse before court starts, usually around 8 a.m. and ask the clerk to send your case to the judge because you missed a meeting and don't want your probation to be revoked.  He'll give you many opportunities to amend your errant ways without going to jail or face other penalties. This has been my experience in California and I would not be too concerned about going to jail or suffer other consequences if you inform the court why you missed the class.  Also emphasize that you have no prior criminal record. And you want to play by the rules at all times.