Two tries at crucial moments proved the deciding factor as St Mary's advanced to the Leinster Schools' Junior Cup semi-final over a resilient Roscrea at Donnybrook yesterday.

The balance of play rarely tipped significantly in either sides favour until the final few minutes. Winger Ronan Doherty and centre Paul Griffin had made the most of the two scoring chances which came their way before captain Michael Ryan padded the score-line with a cluster of points in injury time.

The senior triumph earlier in the week had given Roscrea's confidence a timely boost, inspiring them to grasp most of the early possession. St Mary's, meanwhile, began somewhat nervously as fullback Gary Roche and winger James Clarke were kept busy in clearance duties while their weight advantage in the pack was considerably under-utilised.

Through the powerful work of hooker John Egan and number eight John Phelan, Roscrea continued to advance into scoring territory. Still, they had to wait 24 minutes to claim some points when Steven Miller's penalty sliced the upright and went between the posts.

Just when it seemed they would hold their lead into half-time, St Mary's worked slowly downfield and finished up with a well-executed try almost three minutes into injury time. Simon Gibney took the ball from the scrum and set up the quick exchange of passing from Joey Connelly to Griffin who darted over the line to leave St Mary's 5-3 in front.

Roscrea heightened their efforts for a response with a sustained period of attack after the restart but the St Mary's defence held firm. Then they delivered the conclusive setback to Roscrea with a similarly constructed try 15 minutes from the end. Gibney again sent a running ball from the scrum to Griffin and this time it was Doherty's pace that was adequate to reach the corner.

From there on St Mary's seemed content to hold play around the middle of the field. As the clock spilled over into added time, Ryan still found the opportunity to fire over a penalty and then complete a try scoring run to the line. His own conversion increased the score but it will take a lot more consistency to outplay Belvedere in the semi-final.

St Mary's College: G Roche; J Clarke, M Ryan, P Griffin, R Doherty; J Connolly, S Gibney; D Good, O McCormack, D MacNally, F O'Sullivan, C Lennon, R Timmons, G O'Donovan, P Spillane. Replacements: B Higgins for Good (26 mins), P Brophy for Gibney (51 mins).

Cistercian College, Roscrea: S Millar; A Wrafter, P Brady, C Phelan, J Hughes; E Kelliher, A Smyth; P Fleming, J Egan, O Cavanagh, N Byrne, D Hoctor, L Maher, P McIntyre, J Phelan. Replacements: M Kenny for Fleming (37 mins), D Corcoran for Maher and H Maloney for Wrafter (45 mins).

Referee: D Keane (ARLB).