Cael Chanders was the hero with a last-minute try, converted by Mark Young, to snatch the Leinster Rugby Junior League from Gonzaga at Energia Park by 26-24.
Newbridge centre Calum Corcoran was the first to find the line and full-back Young converted in just the first minute.
Gonzaga came right back and hooker Tim Cotter claimed a try in the fifth minute.
The Sandford Road school were relentless, forcing Newbridge's Young into a try-saving tackle on Charlie Thomson which just delayed the inevitable breakthrough from No 8 Noah Maguire. Out-half David Colbert made it 12-7.
Gonzaga got the scoreboard separation they were after when swinging the ball right and left for centre Hugh Goddard to split the defence for 17-7 in the 34th minute.
The flashes of excellence from the Kildare boys reappeared with centre Corcoran and Young setting up left wing Harry Farrell for a muscular finish on the left.
Gonzaga centre Hugo Neville showed his power in scoring a try which was converted by Colbert for a double-scores advantage, 24-12.
Newbridge captain Kelly then twisted for a try which was converted by Young in the 54th minute.
The excitement grew all the way to the end as Chanders grounded the ball at the butt of the left post. It was left to Young to convert in the last act of a most dramatic final.
Scorers - Newbridge College: C Corcoran, H Farrell, K Kelly, C Chanders try each, M Young 3 cons; Gonzaga College: N Maguire, T Cotter, H Goddard, H Neville try each; D Colbert 2 cons.
Gonzaga - Hugo McLaughlin; Stephen Higgins, Hugo Neville, Hugh Goddard, Charlie Thomson; David Colbert, Charlie Breslin; Tomás Noone, Tim Cotter (Toby Hammond 46), George Morris (Patrick O'Brien 59); James McCarthy, Luke O'Callaghan; Darragh Geraghty, Paul Wilson, Noah Maguire (capt).
Newbridge - Mark Young; David Grant (Patrick Gaire 54), Calum Corcoran, Lucas Berti Newman, Harry Farrell; Robert Dillon (John Collins 54), Tadhg Brophy; Finn Mahon, Tom Waters (Samuel Fitzgibbon 35), Harry Rigney (Max Barry 57); Denis Dowling, Cael Chanders; Patrick Stapleton, Ruairí Byrne, Kieran Kelly (capt).
Ref - R O'Flynn (Leinster Branch)