In South Carolina, ATV drivers must be at least six years of age. Drivers 15 and under AND without a driver's license are not allowed to carry passengers, and must complete an ATV safety course prior to any driving. Also, drivers 16 and under must not operate an ATV without an adult. They must also wear helmets and eye protection at all times during riding.
Check out these Mc Bee, SC ATV/OHV resources: