He arranged for pupils to put their ideas to Lisa Austin, from Rhondda Cynon Taf council's parks department, and Jo Perry, from green charity Eco-Schools.
"This is unique - children have never put their ideas to us before," said Lisa. Money was pledged to help. The children were spurred into action and have organised a litter pick, painted frames in the park, created posters targeting owners who allow their dogs to foul the park, and the grass has been cut. The children are now raising money for swings and a slide. PC Parker's job now is to prevent further vandalism by making pupils in the local comprehensive aware of what the younger children are doing.
The lesson that sparked all this activity was picked up by PC Parker while taking a course on learning styles - part of his studies for a graduate diploma in education at Swansea Institute of Higher Education (SIHE). He is part of the school community police team who work full-time in schools across Wales to deliver a core programme of personal and social education lessons. These officers are dedicated to full-time work in schools, with each taking on about 29 primary and three or four comprehensive schools.
But long gone are the days when officers delivered a talk on such topics as drugs or stranger-danger. The SIHE course means officers have received high-quality training to equip them for the demanding job of educating young people, and of helping teachers to deliver the statutory curriculum in PSE.
The course is spreading good practice. PC Bev Anderson, from Dyfed-Powys police, used the same lesson on vandalism in an imaginary park in a pupil referral unit. It was a great success with the boys in the unit. The one playing the vandal said: "I had no idea so many people were affected when parks were vandalised."
The lesson is designed to help pupils experience what it is like to create the perfect park - and then how it feels to have it vandalised. Drama techniques are used to ensure all pupils are involved. Pupils also engage in role-play to see how different actors in their park respond to the vandalism, before talking about issues arising from the lesson.
Another officer had dealt with a victim of text bullying, which gave him credibility in the classroom - he knew what he was talking about. Having achieved the graduate diploma, he is now able to plan lessons as well as deliver them. Most recently, he has put together a series of lessons to raise awareness of cyber-bullying, and designed a session intended to make pupils aware of internet safety and how to spot online paedophiles seeking victims.
The school community police officers' scheme and the SIHE diploma programme have received investment from the Assembly government, and provide exemplary models of inter-agency working. Four teachers have been seconded from schools to lead the officers in each of the Welsh forces, and the first successful police graduates completed their courses this summer.
Training police officers to work in partnership with schools to teach the PSE curriculum has proved to be a superb initiative that brings the real-world experience of police officers into the classroom, to the benefit of pupils and teachers.
Evidence of the impact of the officers on schools comes from many sources.
One head said she recently had the best conversation on education since she completed her MA - and it had been with her school community police officer. These officers are breaking down the barriers between the police and communities. Children from four to 16 are learning to trust police and are building relationships that should stand us in good stead in future.
Dr Sue Lyle is head of continuing professional development at the Swansea school of education, SIHE. Chris Mort is a school community police officer insouth Wales