The High School came close to claiming another big scalp at Donnybrook yesterday before Castleknock inevitably wrapped things up to go through to the quarter-finals of the Leinster Schools' Senior Cup.

After their surprise win over 1997 finalists Roscrea College, High School again defied the odds to lead their opponents by a point at half-time.

Their only try was textbook stuff. From a lineout take by Shane Cusack deep in Castleknock's 22, second-row Will Lett gathered to go over with 16 minutes gone. Gary Black's conversion saw Castleknock's lead - two penalties from Simon Crawford - wiped out.

But Castleknock, with the aid of the breeze in the second half, always seemed to have enough up front to regain control.

With 11 minutes remaining, prop John Lyne charged at the High School cover and when the ball was moved out wide, full back Andrew Lynch made the decisive break into the corner.

Crawford added the points and in the dying seconds wing forward Kieron Collins scored another try.

Castleknock: A Lynch; P Daly, C Manning, B Macken, O Threadbold; G Stafford, L Greely; J Lyne, J Reid, C Flynn, P Duffy, K McCabe, D Harris, K Collins, S Crawford. Replacement: R Byrne for Mannings (21 mins).

High School: I Massod; T O'Brien, E McNally, D Foran, C Sookram; G Black, D Campbell; J Maher, R Simmons, I Logan, S Cusack, W Lett, R Burns, J Ellis, N O'Byrne. Replacements: T Bass for Logan (60 mins), J Collery for Simmons (60 mins), S Loane for Burns (68 mins).

Referee: J Dempsey (ARLB).