Something doesn't sound right. What does the possession have to do with driving. It is possible that you got a form type correspondence. Even when you are charged with a traffic violation, traffic school isn't necessary until the time of conviction. You should consult an attorney to review any paperwork and advise you on the best course of action
This does not sound right- however if the court ordered it, go to traffic school. Have an attorney review the papers you received.
ANDREW ROBERTS CRIMINAL AND TRAFFIC TICKET DEFENSE ATTORNEY