St Macartan's Monaghan hit an injury-time penalty to edge a dramatic 2-9 to 2-8 win over St Patrick's Dungannon in the last MacRory Cup quarter-final.
The Monaghan school led 1-6 to 1-4 at half-time but Dungannon looked to have secured victory as they led by two as the match entered injury-time.
However, Macartan's last-gasp penalty set up a semi-fnial against St Paul's Bessbrook on Wednesday, 27 February.
St Pat's Maghera face St Colman's Newry in the first semi-final next Saturday.
The match will take place at Dunmoyle (14:30 GMT) with the second semi-final at the Armagh Athletics Grounds four days later (19:30).