Pupils at a Harpenden infants school took matters into their own hands after seeing the amount of single-use plastics they were wasting.
Now Crabtree Infants School has changed the way school milk is received to help the environment.
Eco teacher Andrea Bootle explained: "Every Friday, our bins were overflowing with little milk cartons. Each child could get five of them a week; each with its own straw. And with 180 children in the infants school, even if only half of them had milk ordered for them, the maths was staggering: 90 children, five cartons a week, 39 weeks a year - that's 17,550 little cartons and straws to landfill a year.
"The children loved getting their milk, but the waste upset them, so we looked at options for recycling the cartons, but since many still contained liquid, we couldn't see a sensible way to deal with the waste.
"With adding in all the plastic shrink-wrap - the waste was extraordinary."
The pupils wrote to the school's designated milk provider who offered them an alternative supply of re-usable plastic beakers and large containers of milk instead of individual cartons.
"Obviously, we were nervous at first. We had visions of milk flooding all over the carpet if they used open beakers. However, all the staff have been amazing and the children have coped with it well."
Reception teacher Georgia Frost said: "The children in reception enjoy socialising at the snack table. They have gained independence by pouring their own milk, whilst being eco-friendly.
"It allows them to take some responsibility for the whole world around them; something we encourage in all aspects of school life."
Andrea added: "The children were so right to challenge what we do. Their determination has saved thousands of cartons and straws from ending up in landfill. I'm extremely proud of them."
Now the team behind St Albans Sustainability Festival is using Crabtree's example to encourage teachers from across the district to get involved in this year's Schools Week, which is running from June 1-5 as part of the wider two-week event.
SustFest has a schools working group with representatives from a number of local organisations as well as climate education specialists and enthusiasts from across the district.
Group chair Isobel Mitchell said: "We would love all schools in the district to register for the Sustainability Festival Schools Week - whether with a small event for an eco-team or a whole week of events - everyone is welcome!"
This year London Colney schools are organising a walk to school week; Samuel Ryder Academy is using plastic bottles to build a school greenhouse, Fleetville Infants is holding an eco week, and Abbey CE VA Primary School is working on its outdoor learning environment.
For more information on sustainable schools and taking part in the festival see https://sustfest.org/schools-youth/
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