Summer’s ending and school’s recommencing — and along with the sound of bells ringing comes the simultaneous groan of kids nationwide. But this year, more American students than ever will return from vacation to a new backdrop, a green schoolhouse.

Yep, the little red school-house of yesteryear is getting a redo, making way for a 21st-century incarnation. Of this country’s 100,000 private and public schools, approximately one a day are now registering for LEED certification, according to the U.S. Green Building Council (USGBC).

These little green schoolhouses still teach the “Three R’s” (reading, ‘riting and ‘rithmetic), but they’ve added three more – “Reduce, Recycle, Reuse.” And they’re doing it not just through energy-efficient building principles or water-conserving whiz-bangs, but through curricula, community-outreach projects, cafeterias, landscaping, new buses and transportation policies. One school in Oregon, Clackamas High School, has a city-wide cellphone battery recycling program and last year planted its own orchard.

The greening of America’s schools is a phenomenon to behold. Less than four years ago, Arizona and Washington state were two of the first to require all new public building construction meet LEED Silver requirements. Now dozens of states have green ground rules for schools. New York prohibits the use of non-green cleaners, while its neighbor New Jersey has mandated that all new schools be built to LEED specs. The 58 member schools of the Kentucky Green and Healthy Schools Program marked the project’s first anniversary this year (Kentucky made national news when it banned the sale of non-cafeteria foods on campus a couple of years ago).

Even foot-dragging Washington D.C. has gotten involved. The U.S. House Representatives created a Green Schools Caucus last November and now has more than 50 members. Earlier this summer, the House passed a bill that, if dovetailed with a similar Senate one, would fund $20 billion over the next five years. Known as “the 21st Century Green High-Performing Public School Facilities Act,” it would help states construct new schools or renovate existing ones to make them healthier, more energy efficient and better for the environment.

But the numbers say it all. Since 2007, when the USGBC launched its LEED for Schools –- which has additional specs for things like acoustics and mold control (see USGBC for specs)– more than 78 schools have been certified and more than 750 have registered for certification. Its Green Schools Map illustrates how wide-spread the greening of America’s schools has become.

One of the first was the 220,000-square-foot Desert Edge High School campus (pictured left), part of the Agua Fria school district outside of Phoenix, in the burb of Goodyear. Built in two phases between 2002 and 2005, with the second, complementary phase turning out its first graduates in 2006, Desert High was the first school in Arizona to receive a LEED Silver rating, the fourth in the country and, according to multiple sources including the U.S. Department of Energy, the fifth in the world.

Since then, Agua Fria has built a second, even greener school, Verrado High (pictured right and far top), which opened in 2006 and is awaiting its LEED approval. (No problem, says the district’s assistant superintendent John Schmadeke. “We’re certain that will be another one.”)

In fact, since undertaking the Desert Edge extension, the entire school district has greened up its act and is waiting for the funds to build a third uber-green (LEED Silver) high school in 2009 or 2010. Already, Desert Edge has received kudos nationwide, such as The Green Guide’s most recent “Top Ten Greenest Schools” (2006), as well as special recognition from Arizona Gov. Janet Napolitano.

“All that’s really cool,” adds Schmadeke, who was in on the ground floor of his community’s ambitious mission. “I mean, these things kind of come and go, but we’re really in it for the kids. We keep making it better for them –- the best we can. But what matters is graduation rates and kids getting a good education in a healthy environment.”