A police officer was hospitalised while trying to break up a mass brawl involving school students in the Hastings suburb of Flaxmere today.

The officer was one of many from the Hastings area deployed to Flaxmere Park about 3.30pm when fighting broke out among a mob of about 200 students from two local high schools.

Acting Senior Sergeant Cory Ubels said when officers initially arrived to try to break up the fighting two were injured, with one requiring hospital treatment.

"A large number of police officers were called in from around the area in order to control the students and bring the situation under control," Mr Ubels said.

He said there were seven arrests - all aged between 13 and 15 - and a 14-year-old would appear in Hastings Youth Court tomorrow charged with assaulting police.

"The other six youths will be referred to police youth aid charged with disorderly behaviour likely to cause violence."

Mr Ubels said a 13-year-old was also arrested after being found with a chain.

He said police were investigating the incident to try and find out why the fighting took place and who the ringleaders were.

- NZPA