There's an evangelical streak to pupils at Shawlands Academy when they get onto the subject of their award-winning "eco club".
"If we didn't do this sort of thing, 20 or 30 years down the line it would really affect people," says Robbie Johnstone, 15. "We have already made enough of a mess - we have to start cleaning it up now."
He is referring not to the drastic reduction in litter at the school, although that has been one of resident environmentalists' big achievements, but to the future of the planet.
Myriam Mouflih, 13, will only be in S2 after the summer, but is already on message: "It's a really important thing, because there might not be a world left for our grandchildren. We can make a difference."
Daniel Chisholm, 16, has been in the eco club since it started in 2004. He stresses that its weekly meetings look beyond the school walls by "projecting the message into families". Other pupils say they have done that by convincing their parents to set the washing machine to 30 degrees or steering clear of products with excessive packaging.
Shawlands Academy won the Greener Schools category at the recent Scottish Education Awards, prompting a visit from the judges of the UK-wide education awards at the end of term. They were impressed by the many ecological initiatives at the school, but it stood apart from others because of the pupils' informed passion for the environment. "The kids were among the most enthusiastic and articulate I have met," said judge Peter Jenkins.
Basia Gordon, the modern languages teacher who oversees the eco club, says: "It is evangelical in many respects."
The pupils' achievements, through 25 members of the eco club and splinter groups involved in forest parks and travel planning, are impressive. They recycled 886 kilograms of paper and plastic in 2006-07, and the tally for the year just past is expected to be far higher.
They have helped regenerate nearby Pollok Park, organised an "eco conference" involving 16 organisations, started a bicycle-hire scheme for pupils and designed two sets of reusable jute shopping bags.
Daniel stresses that the whole school has changed its thinking, not just a small band of activists, pointing to a drastic reduction in litter around the building: "All the pupils are more aware and are actually contributing more."
There is no formal planning process for the eco club, a deliberate ploy designed to encourage creative thinking. Nor does the club exist in a vacuum, with staff and pupils keen to take advantage of the more flexible curriculum being encouraged nationally.
One of the school's most impressive projects was "How to be an active citizen in a clean Europe", an exemplar for A Curriculum for Excellence that combined citizenship and the environment, and was mainly driven by art and modern languages.
It resulted in an ambitious 23-minute video diary - described by Mrs Gordon as "lively, fast-moving, colourful, driven by music, slightly surreal and quirky" - that used six different languages, plus Braille. Mrs Gordon believes the project showed how secondary schools can allow "flights of fancy" and need not be inflexible.
"This is terribly difficult for a secondary school to do - it's far easier for a primary," she says. "There's always a tension between academic attainment and the wider curriculum.
"What it does is promote an enquiring mind, making them think about the wider world and become more rounded individuals."
Pick it up policy
How the eco club reduced litter at the school
A publicity campaign, using the logo "Every little bit helps, every little bit hurts", led to posters throughout the school
A play in French, 'Litterhitters', was staged in Pollok Park
A group of litter collectors was organised and "paid" in vouchers for the school canteen, in an attempt to overturn the traditional view of litter-picking as a punishment and instead highlight the positive contribution made
A "litter strategy" was written for the school
Picnic tables were bought to encourage pupils to use the school's outside area
Members visited Polmadie litter reclamation facility to research recycling
Artwork, including sculptures and posters, formed part of 'Art D'Eco', an installation at Pollok Park
The club visited the Department of Environmental and Rural Affairs at the Scottish Executive to investigate sustainable development.