First, hire an attorney if you can. They can go and appear in court for you and avoid you getting arrested on the warrant! If you can't afford an attorney, I would still walk into court, go to the clerk's office and put yourself on calendar to explain. Walking in on your own instead of waiting until they arrest you will look a LOT better to the judge and he may be willing to just reinstate you in the classes. Plus, have you heard of Prop 47?? Consult with a local attorney (most offer free consultations) over whether or not it might help reduce your charges/apply to you.