RBAI fought from 10 points down to beat Methody 12-10 in the 2005 Renault Ulster Schools' Cup final at Ravenhill.
Inst players surrounded their skipper Andrew Watt after the match
A fifth minute penalty from winger Owen McMurray gave Methody a 3-0 lead.
Then McMurray ran in for a fine try on 23 minutes after taking a pass from full-back Colin Fenton. McMurray kicked the conversion.
Lewis Creighton scored a 49th-minute try which he converted and then Michael Young went over for RBAI's second and match-winning try on 56 minutes.
Methody had the advantage of a strong breeze in the first half and will probably feel they needed more than that 10-point advantage at the break.
TOP SCHOOLS' CUP WINS
22: Campbell Coll
9: Coleraine AI
9: Royal Armagh
6: Portora Royal
5: Bangor Grammar
They looked well on their way when McMurray racked up those 10 points but failed to add to that tally.
Inst fly-half Lewis Creighton could have cut the deficit but saw a penalty come off an upright.
But Creighton launched the RBAI revival when he forced a path through to score under the posts.
Creighton was involved in the second try as well, offloading for Young to burst over the line.
It was an emotional day for winning captain Andrew Watt whose mother had died six days earlier.
"He is an absolutely outstanding captain," said Inst coach Brian McLaughlin.
"His mother died on Friday and he was at training on Saturday morning.
"He is a credit to all the lads in the school and to his mother and father."
McLaughlin described the final as a real thriller.
"It was nip and tuck with both teams giving their all," said McLaughlin, after his fifth cup triumph as RBAI coach.
"The Methody guys did their school proud. We were ruthless and took our chances when they were there."