St Munchin's edged their Limerick rivals Ardscoil Ris in a pulsating clash to advance to the semi-final.
There was nothing to separate the two sides in the first half and, after Munchin's missed two early penalties, Ardscoil scored the first try of the game through scrum-half Colm Noonan. Robbie Burke added the extras.
Munchin's weren't behind for long, however, and hit back with a try of their own when Peter Meyer burrowed his way over the line. Shane Airey slotted the conversion, to leave it 7-7 at half-time.
Fifteen minutes after the restart Ardscoil Ris regained the lead after Ronan McKenna crossed in the corner for a fine try.
But, once again, Munchin's refused to lie down and were behind for just five minutes. Burke's kick was brilliantly charged down by Dan Goggin, who touched down under the posts.
Airey added his second conversion of the afternoon for a two-point lead.
Two minutes later, Munchin's scored the crucial try that saw them home.
After a well worked line-out, Munchin's' maul, which was outstanding all afternoon, drove captain Lee Nicholas over the line.
Ardscoil fought right to the death but couldn't find a way through a resolute Munchin's defence.
The Corbally school now face Rockwell in the semi finals and this will be a repeat of last year's final.
St Munchin's College – S Halpin; E O'Keefe, D Goggin, D Kelly (S Doona 53), G Bateman; S Airey, R Meagher; D Begley, P Meyer, B Keogh (J Prendeville 53); S O'Mullan (K Browne 53), T O'Dwyer; L Nicholas (capt), J Sheehan, B Kilkenny.
Ardscoil Ris – S Fitzgerald; C Ryan, R McKenna, R Deegan, B Moriarty; R Burke, C Noonan (J Murray 61); T Cusack, J O'Halloran, C Glynn (capt) (K Brown 61); F Bradshaw-Ryan (S Fenton 46), P Kearns; C Flanagan, P Obande (Ryan 53), C Irwin.
Ref – B O'Connell (MAR)