Surveys were carried out in May at rrimary schools around the UK as part of the BBC's Terrific Scientific intiative, the Trees strand of which was run by environmental group United Bank of Carbon (UBoC) and the Leeds Ecosystem, Atmosphere & Forest (LEAF) Centre, both based at the University of Leeds.
Pupils found out why trees are important for the climate, oxygen, biodiversity, flood prevention and air quality. They then surveyed trees growing in or around their school, recording number, species and height to derive a figure for carbon storage.
Over 6,000 trees were counted during the investigation and more than 2,000 of them were measured and identified. This revealed that the median number of trees per school was 30, regardless of whether they were urban or rural, though 4% of schools had no trees at all.
The majority of the trees surveyed were below 10m in height, while the tallest was 30m. The broadest had a girth of 5m.
The children estimated that the trees they surveyed contained a total of around 550 tonnes of carbon, equivalent to the annual carbon footprint of 275 people living in the UK.
Extrapolated to all 25,000 primary schools in the UK, trees in UK primary schools are estimated to have removed around 400,000 tonnes of carbon dioxide from the atmosphere over their lifetimes - though this equates to just 0.1% of the amount of carbon dioxide emitted by human activities in the UK every year.