It was always going to be a close contest between two of the top teams and that's how it turned out as Armagh Royal School qualified for the semi-finals of the Danske Bank Schools' Cup with a 17-14 victory at Ballymena Academy.
Both teams played their best rugby into the strong wind as the visitors took a 17-11 interval advantage.
Armagh kept the ball tight into the elements and made ground with their short-range passing.
They went in front with a Romain Morrow penalty which was cancelled out by Ballymena's Ross McKay before sustained pressure and recycling opened up a gap and visiting tight-head prop Jude Roberts crossed for Morrow to goal.
Academy then made ground into their opponents' territory and winger Paul Gosher touched down far out.
Armagh's second try was similar to their first as they wore their opponents down for Sam Rainey to run in a second converted score. McKay kicked a second penalty but Armagh warranted their six-point interval advantage.
Ballymena coach Gavin Murray felt the scoreline was a fair reflection of the game but admitted that his team needed to play some real rugby into the wind.
"We came out fighting but credit to Armagh, who defended stoutly. It was a hard struggle and we only managed one more Ross McKay penalty," he said.
Armagh coach Chris Parker was pleased that they came away with a victory as he felt home advantage made Ballymena favourites.
"We played well in the first period but failed to make full use of the wind after the restart," he said.
"We struggled to look after the ball and Ballymena came at us really hard. They were on our line a few times but thankfully we managed to keep them out.
"It was a satisfying result but there is a lot of work to do before the semi-final."
Ulster Schools' U18 No.8 Callum Smyton scored two brilliant tries for Enniskillen Royal but it was Wallace High who earned a semi-final place with a 19-10 win. The Lisburn team's scores came from Finn Rankin, Cameron Doak and Peter Heasley with Nathan Doak converting two.
RBAI have had the easiest trip into the semi-finals having avoided the other seeded teams but now the competition really starts against Armagh.
With home advantage again, they proved too strong for Friends' and triumphed 52-12.
Ronan Boyle contributed 22 points with a try, conversions to all seven tries and a penalty. The other scorers were Hugo Ellerby, Oliver Metcalfe, Joshua Patterson, Jack Leathem, Rory Adair and Jude Postlewaite, while Friends' Reece Malone goaled one of the tries from Fergus McEwen and Stuart Patterson.
Danske Bank Schools' Subsidiary Shield: Down High 17 BRA 14, Coleraine Grammar 20 Grosvenor Grammar 19, Ballyclare High 10 Bangor Grammar 17. Cambridge House v Campbell College postponed.
Danske Bank Schools' Bowl semi-finals: Limavady Grammar 3 Dromore High 17, Belfast High v Banbridge Academy postponed.
Danske Bank Schools' Trophy semi-finals: RS Dungannon 18 Omagh Academy 17. OL and St Patrick's v Larne Grammar postponed.