RBAI made up for Monday's disappointment when they defeated Campbell College in the Schools' 3rd XV final at Pirrie Park.
Inst deserved their victory as their opponents failed to play to expectation.
It was the Inst pack that paved the way to success and helped them take a six points advantage at the interval when Cameron Black kicked two penalties.
The Malone Road side made it 9-0 before Campbell reduced the arrears with a Kashmir Yandell penalty.
This gave them the incentive to attack and they took up a position close to their opponent's line.
The Inst defence managed to keep them out and a clearance kick by Aly Hill brought play upfield. Scott Coates gathered and made space and kicked ahead.
From the turnover the ball was passed wide and winger Callum Blundell crossed for the only try of the tie.
It was a closely contested encounter but Inst had the edge.
The final of the Danske Bank Schools' Subsidiary Shield is at Ravenhill this afternoon, 2.30 pm.
Campbell College who were eliminated in the fourth round of the Schools' Cup by the eventual winners Methodist College 12-0, start favourites to repeat their earlier season victory over BRA.