Catholic University School completed the semi-final line-up with a comprehensive victory at Terenure College.
It was mostly one-way traffic as right wing Mikey Holloway struck twice for tries to create a 10-0 lead at the interval.
And the misery continued for Pres Bray as CUS full-back Conor Byrne added another brace in the 37th and 44th minutes to double the advantage.
Centre Mark Dent burst over for the fifth try, converted by out-half Sean Cox, and CUS were safely through.
Pres found some reward for their efforts through an unconverted try by left wing Nathan Hamilton in the 56th minute.