On any probation violation, the Defendant is always looking at the original time he could have received on the underlying offense. For instance, let's say the Defendant was placed on probation for 5 years on a 3rd degree Felony, which is punishable by up to 5 years in prison.
During the term of probation, he gets violated in the 3rd year of probation, so the most amount of time the Defendant can receive on the violation is 2 years because that would be the most amount of time he could have received on the underlying charge, or 5 years.
While you didn't violate for drugs or alcohol, you did not complete several terms and conditions of the probation. The DUI class is often the largest single violation because it speaks directly to the issue of your conviction; DUI.
You are now set for a hearing on the violation. The standard is lower then for a trial and the judge can find you violated simply because you didn't do what was required. However, to violate your actions had to be willful and substantial. If you do not have the money to complete DUI school and fines/costs, make it known to the judge with a financial affidavit (your income and bills). If you work long hard hours to make that little bit of money, leaving no time for community service, make that known (bring in paystubs with hours worked shown). Perhaps an argument of non-willful violation will make the judge more sympathetic to your situation.
In the end, it is up to the judge to give you a possible jail sentence that will not exceed the maximum (1 yr) minus what you have already served. Not knowing how much time of that possible one year max. is left, I don't know how much time you have left on probation to possibly complete all the outstanding terms or do in jail, but that will figure into it. For example, if you have six months to go and say you can get all the terms done in six months, perhaps you can be re-instated (put back on probation). If you have only one month left you cannot possibly complete everything but the judge can only send you to jail for the remaining month.
You may get an offer before the hearing - admit and take the offer or go to the hearing. If you choose the hearing, make your situation known, bring documentation where possible, emphasize the things you have done, and hope for the best. Good luck!
If it is a first time DUI, the maximum amount of time you could do is 6 months in jail; second time= 9 months. It is not likely you will get the max, but you could be put back on probation and told to finish the program. Also, it sounds like to me you may have some defenses to the violation. You may not be guilty due to your inability to pay.
Sign up to receive a 3-part series of useful information and legal advice about DUIs.