Lewis Jones took victory after a dramatic race as long-time leader Joe Ellis and polesitter Jacob Stephenson crashed out on the final lap.
Ellis, who had led the first five laps before hitting the front on the penultimate lap, crashed out on the final corner along with Stephenson, as Jones took the win by 0.378s from Jack Kirsch.
Third was Lennon Docherty, with Finn Smart-Weeden fourth as Kalvin Kelly rounded out the top five.
HEL Performance British Junior Supersport Championship with Motocourse, Race Two result:
1. Lewis Jones (Symcirrus Motorsport)
2. Jack Kirsch (RD Racing) +0.378s
3. Lennon Docherty (Symcirrus Motorsport) +0.585s
4. Finn Smart-Weeden (Wrapped Racing by Club 74) +1.181s
5. Kalvin Kelly (Completely Motorbikes Kawasaki) +1.188s
Championship points after Round Four:
1. Lewis Jones 94
2. Finn Smart-Weeden 81
3. Jack Kirsch 76
4. Kalvin Kelly 64
5. Jacob Stephenson 59