This is how our schools work. We have full morning of class, but the last class of the day is a final for one class period. Then three half-days for the finals in the other periods and you only have to show up if you have final. Essentially you can be done on the last day of normal classes if you're exempt. Seniors have to finish their state required classes (Gov and English) before hand because you have to pass them to graduate, so those finals are a week before the school wide final.
I think most VA schools still open post Labor, at least in NOVA, though I'm sure there are some schools in southern VA start earlier.