Firefighters were called to Wilmslow High School at 10.57pm on Friday, 5th August.
Upon arrival they discovered chairs were on fire on the school playing field and it was believed they were deliberately set alight.
Firefighters used a hose reel jet to put out the blaze and are appealing for anyone with any information to call Crimestoppers, anonymously, on 0800 555 111 or Cheshire Police on 101.
