The children have already found out which predators are at their school and on some of its neighbouring properties. They discovered a lot of hedgehogs and weta, and some rats and mice. Results from Virginia Lake look similar.
Hedgehogs count as pests because they eat the invertebrates (insects, including native weta) that are food for some birds, St John's Hill acting principal Kevin Booth said.
Virginia Lake Trust chairman Terry Coxon gave the group $500 for the tunnels used there.
He said he would like to know how many predators are at the lake.
"We know there are big rats, and vermin that rob the swans' and ducks' nests, and feral cats, but we have no idea how many of them."
If the trust and council agree, the children could go on to place kill traps, securely enclosed in boxes, at the lake reserve.
The idea is to encourage more people to keep predator numbers down by having traps at their homes.
Brunswick and Westmere schools and Whanganui City College are also involved in the Schools Halo Project.
It's part of Predator Free 2050, a project to rid New Zealand of its most damaging predators. In Whanganui the Bushy Park Education Group is overseeing the halo schools.
The Bushy Park Sanctuary has its own halo project, with predator control happening on properties surrounding it.
