school playgrounds

My 6 year old son discovered adult magizines on the overbrook school playground during gym, this is very disturbing on so many levels I contacted the school the police and the board of ed another mother and myself cleaned the playground today and discovered many more discusting things including adult toys magazines and drug parafanailia hopefully the playground will stay clean and our children wont be exposed to anymore horrible things how can we prevent this from happening again the police said the would patrol and the space under the slide has been boarded up I applaude the school for their quick actions in this matter the principle is great but the town need to keep people off the property before during and after school hours