Royal School Armagh reached their first Danske Bank Schools Cup final since 2004 by ending RBAI’s three year reign as champions in a dramatic game at Kingspan Stadium.
Willie Fallon’s side outscored Inst by four tries to three and will meet Campbell in the decider on Monday, March 19.
Armagh had an early chance to score after Inst knocked on from the kick off in their own 22, but the Belfast side were able to win the resulting scrum against the head and clear their lines.
Armagh wasted another chance to break the deadlock when they won a penalty in midfield but centre Zac Thompson’s long range effort drifted wide.
Royal School spurned another chance when they forced an attacking five metre scrum, from the base they released centre Matthew Reaney but he knocked on with short of the try line.
Armagh finally made their territorial and possession dominance count on 16 minutes. Fom a lineout the forwards rumbled for a few metres before spinning it to Reaney and the centre burst through the midfield defence to score under the posts with Thompson converting.
Armagh doubled their lead on 18 minutes with another converted try.
They kicked a penalty to the corner and from the lineout the forwards mauled before the ball was moved through the hands. Armagh patiently worked the ball through a number of phases before hooker Jack Treanor powered over from close range with Thompson.
Inst opened their account on 28 minutes with a penalty from centre Robin McIlveen from in front of the post after Armagh were caught offside at a ruck.
Inst got back into the game four minutes before half time when they forced a penalty close to the Armagh line and elected to take a scrum.
From the base scrum half Niall Armstrong made a sniping break and glided over unopposed with McIlveen’s conversion cutting Armagh’s lead to 14-10 at the interval.
Armagh should have increased their lead five minutes after the restart; following a powerful driving maul from a lineout the ball was flung wide but winger Nicholas Jennings was held up over the line.
From the resulting five metre scrum Archie McAlpine was held up but it was time lucky for Armagh when at the next scrum No8 Ryan O’Neill picked up and powered over with Thompson converting.
Inst winger Josh Postlethwaite finished off a slick handling move in the corner on 49 minutes but McIlveen failed to convert.
Armagh got their fourth try on 57 minutes, after being held up twice over the line from the third scrum they moved the ball through the hands and Jennings went over for an unconverted try in the corner.
Inst hooker Connor McCormick set up a grandstand finish when he rumbled over from close range and McIlveen converted to make it a four-point game with five minutes remaining.
Inst forced a penalty with the final play of the game, they elected to tap and go but were held up over the try line.
RBAI: B McNamara, J Mullen, R McIlveen, A Angus, J Postethwaite, D Lyttle, N Armstrong, E Sloan, C McCormick, J Wait, D Eakin, T Lyons, AJ Hussell, J Magee, D McCann
Replacements: R Adair, R Curry, S McAuley, T Lavery, A Weir, M Manso, K McComiskey, J Heyburn
RSA: M Campbell, O Webb, Z Thompson, M Reaney, N Jennings, R Morrow, C Worth, J Chapman, J Treanor, J Agnew, R Finlay, S King, A Woods, G Crawford, R O’Neill, S Rainey, A Edgar, A McAlpine, J Roberts, J King, A Johnston, C Whiteside, P Taylor
Referee: D Carson.