"It puts them back for next season's cricket pitch ... and a lot of kids love their sport and want the turf to be in top order."
The school had installed security cameras and tried to block access to the area, as well as contacting police, he said.
"We've put measures in place that should restrict that access and make sure that any opportunity for this to happen ceases.
"There's always a cost around that and we would prefer it if people would show some common sense.
"We just hope people can be reflective and use their energy in more positive pursuits."
He urged anyone who saw anything suspicious to contact police and the school.