A high school in Pickering, Ontario, has been singled out by the Global Coalition for Green Schools as the 2015 Greenest School on Earth.

The Coalition is an initiative of the Center for Green Schools at the U.S. Green Building Council, which made the announcement last month. Dunbarton High School has some 400 students in grades 9 through 12. Pickering is on the shores of Lake Ontario about 20 miles northeast of Toronto.

Schools were judged on what the USBGC called the “three-pillar definition of a green school:” its efficient use of resources and reduced environmental impact; its enhanced health and learning among students, teachers and staff; and its emphasis on sustainability and resource-conservation.

There were 40 applicants from around the globe this year, said USGBC spokeswoman Ali Peterson. “Dunbarton is not a net-zero or a net-zero ready building, but through the programming they have with the students and the community they are making significant progress toward having net-zero impact on their local environment, and the panel of judges deemed them the best example of a school working toward this ideal,” Peterson wrote in an email.

Among the initiatives there is an organic waste collection service in which students collected organic waste from staff offices each week and took it to nearby homes where it’s picked up by the city. Next year, the program will expand to include a weekly collection of organic waste from the school cafeteria.

The school building was renovated over the last seven years

Dunbarton High School was built in the 1960s, and has undergone a “significant retrofit” over the last seven years. Upgrades included new energy-efficient windows, insulation, and a more efficient compressor for an air conditioner. A solar hot water system now serves half of the building.

Hallway lights were replaced with lower-wattage bulbs and better reflectors, and some lights are now automatically dimmed when sunlight is bright. It has an outdoor classroom for 40 students, and a 500-square-meter pollinator garden.

The school also won the 2014 Greenest School in Canada competition. The building is not certified under the USGBC’s LEED program.

Thomas Mueller, president and CEO of the Canada Green Building Council, also cited the school’s engagement with the community and a curriculum that emphasizes “the value of protecting and restoring ecosystems.”

The school was awarded a cash prize of $1,000, which it said would be used to develop a school garden and 10 more “bee condominiums” that would be shared with the community, the USGBC said.