A building made of tires and glass and plastic bottles, off the grid and non-polluting: a village in Uruguay is home to a fully sustainable school -- and a bold experiment in green citizenship.

On this winter morning in the southern hemisphere, the temperature is 7.5 degrees Celsius (about 45 degrees Fahrenheit) in Jaureguiberry, a tiny community of 500 inhabitants an hour's drive east of the capital Montevideo.

But inside primary school number 294, which opened a few months ago, the air easily rises to a mild 20 degrees.

"We are doing fine, with a more than 50 percent charge only from solar energy," said Alicia Alvarez, 51, the school's director, pointing to energy storage units.

"I turned the light down a little so as not to waste it," she said.

Opened last March to children between the ages of three and 12, it claims to be the first public school in Latin America that is totally green.

The school is not connected to the national electricity grid.

From the outside, its environmental bona fides are evident: colorful recycled tires at the entrance, solar panels covering its roofs, big windows overlooking kitchen gardens.

Behind the project is the US architect Michael Reynolds, 70, known as the "garbage warrior" for his long career in building self-sufficient projects with discarded products.

Reynolds developed what he calls "Earthship Biotecture" -- buildings designed to independently sustain human life.

He has built "Earthships" all over the world, from the US state of New Mexico and Easter Island in Chile to Ushuaia in Argentina and Sierra Leone -- though he has faced naysayers along the way.

"People called me an idiot: building with garbage, what a fool, you're a disgrace to the architectural community," he told AFP.

"You know, I was trying to contain sewage and treat it and do all of these things that architects didn't do."

- 'School full of life' -

In Jaureguiberry, about 2,000 tires, 3,000 glass bottles, 1,500 plastic bottles and 12,000 cans were put together with wood, glass and cement to fashion the new school.

The project, supported by a local charity and a detergent company, is estimated to have cost $300,000, according to Uruguayan media.

Though it can accommodate 100 students, for now the school has 39, with a wide range in ages. Some are just starting out in preschool and others are in their final year before university.

All of them are excited to be in a school so unique and close to nature.

"It's a school full of life," said a smiling Paula, seven, who was concocting with her friends a list of things to do, and not to do, to take care of the planet.

This morning, in the class led by teacher Rita Montans, 45, the students are participating in a workshop of creative writing and brainstorming on the theme of environmental protection.

Each offers a proposal. "Don't throw away trash." "Protect plants."

"Don't throw out bottles."

"If there weren't any trees, we'd no longer be there," declared seven-year-old Sebastian.

The aim, according to the teacher, is to create a code of conduct to follow. "Green crosses" are awarded for good practices.

- From garden to kitchen -

The school is a good example: It produces no waste and, across from the three classrooms, the compost-fed kitchen garden brims with basil, tomatoes, strawberries and chard.

On the roof, rainwater is collected then filtered before it is used in the garden or the toilets.

The teachers have special training so they can adapt their courses by tying them to respect for the environment and the responsible use of the building and its energy.

Once a week, the children devote an hour to the garden, picking fruits and vegetables that they have planted and raised, and which they will eat in the canteen.

Sebastian said he had cooked cherry tomatoes. "They are good!" eight-year-old Felipe raved.

"There is no better learning than to experience things for yourself," said Alvarez, the director.

No matter how these students apply their lessons in the future, one way or another, "the seed is already planted", she said.