Methodist College Belfast won 19-3 over Wallace High to set up a Danske Bank Schools' Cup final meeting with Campbell College Belfast on March 18.
The Belfast school, the favourites for the title, triumphed thanks to a brace from openside flanker Adam Reid and a further score from full-back Ethan McIlroy, who kicked another four points from the tee.
Wallace's sole score came from a second-half penalty from scrum-half Nathan Doak, son of former Ulster player Neil.
Methody set the tone early, camping themselves on the Wallace line from the outset, however some strong defence from the Lisburn school kept them at bay.
But on the stroke of half-time, the competition's most successful side forged ahead when Ulster U19 winger Chris Larmour surged up to just shy of the line, with Reid crashing over from close range a few phases later.
Doak reduced the gap early in the second half when he converted a penalty, but that would prove to be their only score as Methody sealed the win.
Reid grabbed his second when he picked and went off the back of a ruck following a strong carry from captain Kevin McNaboe, a score which effectively ended the game as a contest.
And McIlroy added some gloss to the scoreline, the full-back running in after centre John Fletcher made a nice break up the middle and supplied the pass.
Here's the game as it happened: