Police and security staff had to separate the Francis Douglas Memorial College and New Plymouth Boy's High School supporters following their annual match at Yarrow Stadium this afternoon.
The schoolboy teams were playing in a curtain-raiser before the Super 15 Chiefs v Waratahs game.
Trouble broke out on the terraces after the final whistle when Francis Douglas supporters taunted their rivals after their 20-17 victory.
The incident was over quickly, although there will be ramifications.
The two groups of supporters, mostly students, were close together in the terraces and although there had been plenty of vocal support there was no trouble until the match ended.
Police are believed to have arrested at least one person.