Ordinarily, possession of alcohol by a minor (under 21) is not an offense that can be dismissed after traffic school.
It's a misdemeanor to possess alcohol if you're under 21. It can have an impact on your criminal record as well as your driver's license.
You should consult with a criminal defense attorney to see if there's a way to work out something short of a conviction.
A minor in possession of alcohol is not something that traffic school is permitted. It is a misdemeanor and can impact your license and criminal record. Hire an attorney to walk you through this and perhaps obtain a better deal than having this on your record.