In Musgrave Park, Christian Brothers College were 11-8 winners over arch-rivals Presentation Brothers College and in Lansdowne Road, Terenure College defeated St Mary's College 3-0 with a 50th minute penalty.
Inspired by Mark Hill and Chris Henry, Wallace HS dominated an opening half against the pre-match favourites whose line-out just didn't work and they deservedly led 7-3 at half time.
That situation improved for them five minutes after the re-start when Thomas Shorten landed a penalty for a 10-3 lead.
However, a little piece of magic from RBAI full-back Johnny Burgess changed the whole aspect of the match minutes later.
Down south, over 7,000 packed into Musgrave Park to see CBC win the senior title. They led 6-0 at half time thanks to a penalty and drop goal from out-half Eamon Ronan and improved on that with a James O'Hanlon try early in the second half.
PBC clawed their way back into the game with a Brian Barry try and a penalty from Tom Gleeson but CBC clung on for a narrow but deserved win although they had to survive a late PBC surge from a lineout that ended in accidental offside and a relieving scrum for the eventual winners.