The third annual USGBC Green Apple Day of Service attracted thousands of volunteers who took part in 3,760 projects in the U.S. and around the world.

The service day, part of the U.S. Green Building Council’s Center for Green Schools, urges administrators to change schools into safe, energy-efficient and productive places to learn.

During the Sept. 27 event, U.S. Education Secretary Arne Duncan and his family volunteered at a Washington, D.C., elementary school, assisting with gardening and painting projects.

"At the Center for Green Schools, we’re continually inspired by the dedication of local communities and volunteers to improve the places where our children learn,” said Rachel Gutter, director of the Center for Green Schools at the USGBC. “On this third annual Green Apple Day of Service, we couldn’t be more humbled by the sheer volume of activity to transform our schools and communities. Hundreds of thousands of volunteers around the globe are sending a clear message that where we learn matters. To each and every one of these dedicated individuals we say, thank you.”