Fire at NSW school causes $500k damage

A suspicious fire has caused more than $500,000 worth of damage at a school on NSW's north coast.

The fire at the Nicholson Street high school in South Kempsey completely destroyed two classrooms and a staff room of the Learning Support Unit and was threatening adjoining buildings when emergency services arrived around 9pm on Thursday.

Firefighters put out the blaze, which police are treating as suspicious.