The other teams competing in last night's finals at the Fortune Theatre were John McGlashan College, King's High School and Otago Boys' High School.
Theatre education liaison Shannon Colbert said the winner was selected from three competition rounds.
The three judges awarded points for technique and entertainment.
The winner was King's High. The team will compete in the South Island final at The Court Theatre, Christchurch, on September 18.
The other teams which took part in the competition were Bayfield High School, Logan Park High School, St Hilda's Collegiate School and South Otago High School.
Schools in Southland would be invited to compete next year, Ms Colbert said,
The pupils had attended workshops with Dunedin improvisation troupe Improsaurus at the theatre and schools.
