You could do a Motion Nun Pro Tunc to "turn back time" and ask the court to extend the deadline so you can finish the traffic school Do you have a good reason for not completing traffic school on time, something such as a death in the family or a medical emergency?
Otherwise, I think you might be out of luck.
You have to see if you can get your matter on calendar and request the judge additional time to complete traffic school. As Mr. Hill stated, some courts require a reason before they grant this. If you have an attorney that might help.
ANDREW ROBERTS CRIMINAL AND TRAFFIC TICKET DEFENSE ATTORNEY
Complete the class as soon as possible. Hire an attorney to explain why you finished late and ask for the mercy of the judge.
The information provided in this answer does not create an attorney-client relationship and is not considered to be legal advice.
You may go to the courthouse and ask to see the judge in order to request additional time to complete traffic school.