Oliver Askew kept 14-year-old Kaylen Frederick at bay to score his second win of the USF2000 season in race one at Barber.
Championship leader Askew made a good start but was pressured by Frederick throughout the 30-minute race, which went under caution with 13 minutes remaining while the car of Ricky Donison was pulled out of the gravel at the final corner.
After the restart, Frederick closed right up in the final few minutes, with Askew holding on by just 0.227 seconds at the chequered flag.
Rinus van Kalmthout was only half a second further back as he made it an all-rookie podium in third.
Robert Megennis, winner of the season opener in St Petersburg last month, took fourth ahead of Parker Thompson and Dakota Dickerson.
Calvin Ming, Ayla Agren, Andre Castro and Luke Gabin rounded out the top 10, with BRDC British Formula 3 ace Toby Sowery 11th on his series debut with the Benik team.