Cup favourites St Michael’s took the spoils but St Mary's claimed the lion's share of the glory in an absolute humdinger at a heaving Donnybrook.
This was as good as schools rugby gets. A cup match that had everything, with Michael's using that proverbial 'get out of jail card' like never before.
When the chips were down and their backs were to the wall, they produced a length-of-the-field try sparked by replacement out-half Harry Byrne and finished by scrum-half David Duggan.
They had throughout looked like a team with Blackrock on their minds, as the lighter, smaller Mary's tackled themselves to a standstill.
Despite eventually coming up short, pride was restored as the Rathmines school delivered a performance high on adrenaline and endeavour, with plenty of skill mixed in.
They were heroes one and all but it would be remiss not to highlight centre Mark Fogarty, the catalyst supreme.
Where he went the rest followed with fellow centre David Matthews, flanker Faolan Crowe and scrum-half Derry O'Connor pretty close behind.
They rattled Michael's on six minutes when Matthews brilliantly read and executed an intercept to race clear and score under the posts. O'Connor to added the conversion.
Far from panicking, Michael's responded promptly.
Outstanding skipper James Ryan led the way, and the athletic second-row forced his way over just five minutes later. Barry Fitzpatrick knocked over the easy extras and it was all square.
Ryan is close to unbeatable in the lineout, so Mary's engineered a simple but highly effective kick and chase game, keeping the ball infield where possible, with O'Connor's kicking on the money almost every time.
But Michael's took the lead nevertheless, when patient handling resulted in dynamic hooker Gavin Barrett racing clear for a 12-7 lead.
The Mary's response was almost immediate with both centres, lock Conn Harte-Bourke, out half David Boyle, skipper Niall Curran and wing Sean McCahill all handling in the build-up for the outstanding O'Connor to pounce. The scrum-half converted for a 14-12 lead at the break.
The second half was nip and tuck all the way, Mary's pounding the line for periods, but cometh the hour cometh the men with replacement Byrne and No 8 Max Deegan central to taking play the length of the field for Duggan to replicate O’Connor’s first-half try.
Fitzpatrick converted and despite Mary's again laying siege to the Michael's line, the favourites held firm.
They've had their scare and will be better for the experience.
St Michael's: M Heaney (M O'Shea 57); J Hickey, J Kelly, O O'Meara, T Molony; R Cosgrave (H Byrne 52), D Duggan; R Mulvihill, G Barrett, S Griffin; O Dowling, J Ryan (capt); B Fitzpatrick, G Croke, M Deegan.
St Mary's: N Hughes; S McCahill, D Matthews, M Fogarty (A Schuster 68), J Ryan; D Boyle, D O'Connor; R Fanning, M Hoey, M McCormack; H Fitzpatrick, C Harte-Bourke; N Curran (capt), F Crowe, R Foley.
Referee: N Correll (ARLB).