Right wing Frank van Heerden scored a try with four minutes remaining as Queen's College beat festival hosts KES 20-16.
KES put pressure on Queen's in the opening stages of the match, which resulted in scrumhalf Anthony Rousseau's try.
Centre Ryan Theron kicked a penalty for KES, before Queen's flyhalf Albre Wagener replied with two penalties, as KES led 8-6 at half-time.
In the second half, Queen's attempted to breach the hosts' stubborn defence with little success before KES No 8 Lwazi Monokali continued his try-scoring form with an unconverted try.
Moments later, Queen's quick-tapped 5m from the KES tryline and fullback Olwethu Foslag scored a converted try.
KES again took the lead through a penalty, before Van Heerden snatched victory for Queen's.
In other day three results, Northwood Boys' marched past Graeme College 24-7, Hudson Park beat Parktown Boys' 23-10, Hentie Cilliers eased past the KES Invitation XV 20-10, Eldoraigne saw off Durban High 26-17, Daniel Pienaar claimed a 34-13 victory over Ben Vorster and Kingswood College beat St David's Marist 30-14.
Day 3 results:
Hentie Cilliers 20 KES Invitation XV 10
Northwood Boys’ 24 Graeme College 7
Hudson Park 23 Parktown Boys’ 10
Eldoraigne 26 Durban High School 17
Daniel Pienaar 34 Ben Vorster 13
Kingswood College 30 St David's Marist 14
Queen’s College 20 KES 16
Day 2 results:
Durban High School 33 St David's Marist 10
Eldoraigne 10 Ben Vorster 7
Kingswood College 28 Hentie Cilliers 26
Northwood Boys’ 12 Daniel Pienaar 7
Graeme College 15 Hudson Park 10
Queen’s College 26 Parktown Boys' 15
KES 10 Rondebosch Boys’ 10
Day 1 results:
Hudson Park 53 Hentie Cilliers 10
St David's Marist 19 Graeme College 15
Kingswood College 22 Parktown Boys' 16
Queen's College 50 Northwood 12
Eldoraigne 25 Daniel Pienaar 6
KES 54 Ben Vorster 12
Rondebosch Boys' 20 Durban High School 8
Photo: Matthew Wood/KES