St Andrew's Secondary School defeated defending champions Anglo-Chinese School (Independent) 21-18 in the Schools National B Division rugby final at the Physical and Sports Education Branch on Monday.
Poor weather conditions had forced the final, originally held at the Home Team Academy, to be postponed twice since last Tuesday.
St Andrew's resumed the match on Monday with an 11-8 lead, but ACS (I), who had been undefeated throughout the tournament, started strongly in attack to overtake their rivals and take an 18-14 lead.
However, St Andrew's scored a crucial penalty try, as well as a successful conversion in the last few minutes to win the title.
"We wanted to win and we expected to win," said their jubilant captain Viviyan Philip, 15, who scored 11 of his team's points. "You can't go into a match expecting to lose."