The Lisburn-based school achieved the landmark feat after a 24-15 win over Royal School Armagh at a packed Kingspan Stadium.
After five near-misses in the competition, there would no further heartache this time around as Rio McDonagh (2), James Gould and Luke Dillon scored tries for Wallace.
Here’s some of the best action and celebratory shots from the day.
9. Schools' Cup Final
Charlie Reaney of Royal School and James Gould of Wallace during this afternoon’s final at Kingspan Stadium Photo: Andrew McCarroll
10. Schools' Cup Final
Cameron Cummings of Royal School Armagh scores a try during this afternoon’s final at Kingspan Stadium Photo: Andrew McCarroll
11. Schools' Cup Final
Evan Hughes of Royal School Armagh kicks the conversion during this afternoon’s final at Kingspan Stadium Photo: Andrew McCarroll
12. Schools' Cup Final
Cameron Cummings of Royal School Armagh scores a try during this afternoon’s final at Kingspan Stadium Photo: Andrew McCarroll