It was the last day of school before the winter holidays, and if the class of 10-year-old pupils were anxious to go home and forget about studying, they were not showing it.
The pupils, in Grade 5 at the Raffles International School in Dubai, were watching a short presentation on a screen while their teacher, Peter Milne, stood by.
The short film about water contained some facts that most adults do not know: that millions of people in poor countries die every year of waterborne diseases and that humanity is rapidly depleting its supplies of clean, fresh water.
As the film ended, Mr Milne asked his pupils whether they had any questions, and hands shot up.
The class wanted to know: is there enough water for all people? How much water do we waste? Why do we need to drink water? What would the world look like without it?
With the number of people on Earth growing at an ever more rapid pace, achieving balance between humanity's hunger for resources and the needs of natural ecosystems will become an increasingly important issue for societies, Mr Milne said. If schools want to equip their pupils with the best possible tools to face the future, it is a challenge they cannot afford to overlook. "Surely, it is the most challenging thing we have got, and there are so many simple things we could do to change this," he said.
Saving water and energy, recycling and preserving biodiversity are all concepts that can be taught to children from a young age, said the 46-year-old Briton.
"If you start children very young, this becomes ingrained into their way of thinking," he said. "They almost see it as a crime if someone is hurting nature.
"Children see it very clearly. They do not over-complicate things. With adults, there are so many complications in their lives, they do not take it in as well ... I think adults worry about making changes; they feel they might have to compromise on their lifestyle."
Besides teaching, Mr Milne is also the environmental co-ordinator for the school, supervising activities for all its 1,400 pupils.
For green messages to be accepted, they need to be presented in an interesting manner, he said. One approach employed at the school is integrating the environment into the curriculum so that children are exposed to green messages even as they learn maths or geography.
"The environment covers everything. It is not a subject, it is a way of life," said Mr Milne.
It is also important to give pupils practical solutions. When he first arrived in the UAE seven years ago, the Briton said, he tried to teach children the importance of recycling. After segregating the waste into plastic, paper, cans and other items, the students had to put it back in one bin as there were no recycling facilities at the time.
"If you tell children about a problem, they need to be able to do something about it," he said.
One of Mr Milne's first initiatives at the school was creating a recycling centre. Every month, 100kg of paper is collected along with plastic and cans, he said.
The programme relies on activities out of the classroom - visits to environmental exhibitions, protected areas and camping trips.
"A lot of the children have never been out to the wadis or the desert," he said. "How can they learn if they don't get the chance to get out there ... You can only do so much in a classroom." In January, pupils will plant a garden on the school grounds. The patch of land will feature a wilderness area with a ghaf tree and other native plants, as well as an organic garden.
Mr Milne is planning on setting up as an environmental education consultant and if that were to happen, he would be missed, his students said. "He is keeping the environment, and I like teachers who are keeping the environment," said Lily Baachelerie, 10, originally from France.
Her classmate, Ahmd Musameh, from Jordan, agreed. "Everything he says is exciting," he said.
