BELVEDERE College caused a major shock by defeating defending U19 'A' champions St Malachy's of Belfast at the Arena in Tallaght 60-50.
The Dublin outfit looked to have been on the verge of being swept away by the talent of Malachy's throughout the first half but always managed to hang around until an inspired run, led by game MVP Oscar Moran in the third quarter, saw them lead after being down by as many as 11 points.
Very much in a battle from there on, Belvedere had the superior form down the stretch and used their greater size to superb effect, winning by 60-50 to claim the U19 'A' Boys' League title.
Earlier in the day, Holy Faith Clontarf survived a late barrage of scores from St Vincent's to win their third straight U19 'A' Girls All Ireland Schools League title.
Led by Aoibheann Byrne, who registered 15 points, Clontarf controlled the game's tempo throughout, slowing down a normally ferociously fast St Vincent's attack.
Despite playing the better throughout, Holy Faith had to withstand a nervous closing few minutes when, leading by double digits, Edel Thornton sprung to life and scored eight of her 11 points.
It was not be enough, however, as the Clontarf side got the defensive stops when really needed and pushed on to be deserving winners, 38-31.
The two U16 A finals in the morning saw silverware for Calasanctius College Oranmore of Galway in the boys and Presentation College, Waterford in the girls. For Presentation, the 48-38 win over Ard Scoil Rathangan was sweet redemption following their heart-breaking schools cup final loss to Crescent College of Limerick by just a single point back in January.
Meanwhile for Calasanctius College, the U16 A Boys League final victory over Summerhill College Sligo (70-46) rounded off a superb season which also saw them claim the cup title in January.