St Michael's Enniskillen produced a late comeback to beat St Patrick's Maghera 0-13 to 2-6 in Saturday's opening MacRory Cup semi-final.
An injury-time penalty from Michael Conroy helped St Patrick's Armagh snatch a 2-6 to 0-12 draw against Omagh CBS in the second semi-final.
Goals from Alex Doherty and Eunan Mulholland put St Pat's Maghera 2-5 to 0-7 up against St Michael's.
However, the Enniskillen school hit six of the last seven scores to win.
St Michael's win means the six-time champions will have a chance to win their first MacRory title since 2012 in the decider on 18 March.
The Fermanagh school's semi-final victory owed much to two tremendous saves by keeper Sean Nally to deny Mulholland goal attempts.
Scores from Conor Lane and Caolan Duffy gave St Michael's an early-two point lead before Doherty netted Maghera's first goal directly from a 13-metre free.
Conleth McGuckin, Conleth McShane and Pat Shivers were among further St Pat's scorers as they moved into a 1-4 to 0-3 lead but St Michael's hit the last three points of the opening period.
After Michael Glynn's levelling free, a Doherty point and Mulholland's goal put Maghera four ahead by the 39th minute.
But another Glynn free started a sequence of six straight St Michael's points which included three Darragh McBrien scores.
A McGuckin point on 59 minutes reduced the Enniskillen lead to the minimum but St Pat's could not get on terms as a Mulholland shot was blocked in injury-time.
In the second semi-final, two Simon Garrity points helped Omagh CBS take a 0-4 to 0-1 lead before Daniel Horsfield's Armagh goal levelled the contest just before half-time.
Points from Aodhan McConnell, Garrity and Liam Gray helped Omagh move five clear at 0-12 to 1-4 as Armagh's hopes appeared over.
However, after two Conroy points left only a kick of the ball between the sides, he then slotted his last-gasp levelling penalty after a Michael McGleenan goal attempt had been illegally foot-blocked.
The replay will take place on Wednesday night at the Athletic Grounds [19:30 GMT].