Jacob Stephenson will head the grid at Knockhill after beating Finn Smart-Weeden by 0.011secs with a best qualifying lap of 56.807secs.
Third quickest was Keo Walker, as Lewis Jones ended the session fourth to lead the second row, with Jack Kirsch fifth.
HEL Performance British Junior Supersport Championship with Motocourse, qualifying:
1. Jacob Stephenson (Kevin Stephenson) 56.807s
2. Finn Smart-Weeden (Wrapped Racing by Club 74) +0.011s
3. Keo Walker (Keo Walker Racing) +0.057s
4. Lewis Jones (Symcirrus Motorsport) +0.194s
5. Jack Kirsch (RD Racing) +0.203s