I've checked the online property records, and the service roads are on the school property and are not marked as a street.  Thompson Mill Road, on the other hand, is shown as a street on the online property records.

In Georgia, according to <https://dds.georgia.gov/section-15-continued-pavement-markings>, on a road with two lanes traveling in the same direction, solid double white lines "indicate where vehicles can or cannot cross to access the adjacent lane" and "lane changes are prohibited", whereas dashed double white lines indicate that "vehicles are allowed to cross over to the adjacent lane".  So, for roads or streets, it is like Germany, only in Georgia there are two solit white lines whereas in Germany there would be one solid white line. 

Georgia law concerning roads would not apply to this oval one way two lane service road on school property, as far as I can tell.  I think that the oval service road is where parents and buses line up to drop off and pick up the kids.