They caused the shock of the 2006 Powerade Leinster Schools Senior Cup and St Gerard's repeated the trick on Tuesday by knocking Terenure out again at Donnybrook.
The Bray school's success was not as surprising this time around, but it put an end to hopes at Terenure that they could mark their 150th anniversary by bringing home their 11th Cup.
This was a tight affair from start to finish and was still in the balance when deep into injury time 'Nure worked their way into drop goal territory but Daniel McCormack's effort was blocked by Adam Carroll and their chance was gone.
It was cruel for the Dublin school who had led with five minutes remaining, only for brothers Steve and Jody Crosbie to combine gloriously for Gerard's.
Out-half Steve's grubber kick was beautifully measured for his older brother, who beat Sean O'Loughlin to the ball and gleefully touched down under the posts to level.
Josh Glynn added the conversion and the boys in green and blue were in front and managed to hold on with some excellent defending.
Their reward is a quarter-final date with the champions Blackrock, who came out on top of their clash with Belvedere on Sunday.
Gerard's will know that they'll need to up their game again to take another scalp, but they should have captain Robbie Glynn available after his 13th-minute cameo from the bench as he returned from injury to make an impact.
Gerard's, coached by Evening Herald columnist and former Leinster and Ireland star Eric Miller, led 6-3 at half-time, after 35 minutes that threatened at times to break into free-flowing rugby, but ultimately nerves and rushed final passes let the sides down.
It was compelling viewing as Glynn kicked two penalties to Barry Kelly's one as 'Nure knew they were in for a tough afternoon from the kick-off when Finn Boylan produced a massive hit. Gerard's were initially on top and Jett Desmond threatened the line after six minutes before running out of space and Terenure turned Jack Conan over.
Rian O'Loughlin almost produced a stunning try when he capitalised on a loose pass by scampering up the wing, timed his step inside to perfection and found Dylan Simmonds who was stopped short. In their desperate defence, last year's finalists fouled the ball on the ground and Glynn added his second penalty.
But it was Terenure who emerged the stronger after the break and Kelly levelled within four minutes of the restart with a fine penalty.
Substitute Carroll nearly scored a try against the run of play for the Bray side after he collected Steve Crosbie's finely weighted cross kick and set out for the line, skipping a tackle before being bundled into touch on the five-metre line.
But it was Terenure who would cross first, with a 30-metre break from scrum-half Niall Casey bringing his side into the '22.
Gerard's turned the ball over, but Carroll's clearing kick was partially blocked down into the hands of the excellent blindside flanker Adam Clarkin who barrelled towards the line.
He was stopped short, but second row Geoff Speiran finished the job although Gerard's players protested that he had knocked the ball over the line in scoring.
Referee Barry O'Keefe awarded the try, but Kelly sliced the conversion and the score stayed at 11-6.
That miss would come back to haunt Terenure as Gerard's applied pressure and edged closer to the line.
The brilliant link-up between the brothers Crosbie won the day, as Terenure ran out of time.
Both brothers were central to the win, with Steve using ball intelligently and Jody carrying well throughout.
Clarkin was the standout player for Terenure, and can count himself extremely unlucky not to have another Cup game to display his wares alongside the impressive Geoff Speiran and Sean O'Loughlin.
Scorers -- St Gerard's: Jody Crosbie try, Josh Glynn 2 pens, 1 con. Terenure College: Geoff Speiran try, Barry Kelly 2 pens.
St Gerard's: Josh Glynn; Dylan Simmons, Rian O'Loughlin, Jody Crosbie, Jett Desmond; Steve Crosbie, Conor O'Rourke; Christian McAlinden, Cillian Hayde, Conor Lyons; Finn Boylan, Robin Maxwell; Stephen King, Stephen Hackett-Delaney, Jack Conan. Replacements: A Carroll for Desmond 41, A Bowtell for Boylan 47, R Glynn for O'Rourke 55.
Terenure College: Stephen Lowe; Barry Kelly, Niall Thornton, Daniel McCormack, Sean O'Loughlin; Nathan Lynch, Niall Casey; Bryan Mooney, Barry Elliott, Paolo Soave; Geoff Speiran, Luke Cowhig; Adam Clarkin, Niall Lalor, Eoin Joyce. Replacement: K Simpson for Cowhig.
Referee: Barry O'Keefe (ARLB).