Pupils from Tannery Drift First School in Royston planted two cherry trees as part of the Queen's Green Canopy initiative.
While the scheme was due to finish at the end of the Queen's Platinum Jubilee Year, King Charles extended the scheme until March.
Tannery Drift pupils have already planted trees as part of similar schemes, including more than 30 donated by the Woodland Trust.
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In 2012, the school was given an acorn from the Royal Parks to mark the Queen's Diamond Jubilee, and the oak tree is now growing well in the school's wildlife area.
The school places an emphasis on outdoor learning. Headteacher Mr Greetham said: "Providing the right environment in which children can learn is what I believe helps children to thrive."
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