It's believed he had hidden behind some bushes near the footpath, which ran alongside the school, and took the photos.
A staff member spotted the man but he walked away before he could be spoken to.
As acting principal Ray Green says, "Don't be afraid to contact the police. It's better to report it and be wrong than not to report it and be right".
The man was described as Caucasian, about 60 years old, and at the time was wearing a black wide-rimmed hat.
He also had on tan-coloured pants and a light-coloured fisherman's vest with lots of pockets. He has a deeply wrinkled face, appears dishevelled, with grey curly hair and a beard or other facial hair.
Be vigilant around our kids - a quick call to police and, easily, the hunter becomes the hunted.