The wind is hammering at the school's turbine, pumping a steady stream of kilowatts back into the national grid. The pupils are nearby, ignoring the less-than-tropical conditions to explore long grass and hidey-holes.
Merrylee Primary, which lays claim to being one of Scotland's greenest schools, may sound as if it's in an exposed, rural part of the Highlands - but it's actually in the midst of a 1950s Glasgow housing estate. The building, which pupils and staff moved into earlier this year, was the first school to meet the city council's "sustainable construction policy". Its demands - to be met for around the same price as a traditionally-built school - include reducing rubbish sent to landfill, increasing use of recycled materials, lowering carbon dioxide emissions, and limiting use of energy and water.
The most obvious sign of the pound;7million school's environmental credentials is a wind turbine that stretches to the same height as the floodlights around the school's football pitch, the first at any school in Glasgow.
Project architect Catherine Cosgrove, of Austin Smith: Lord, said there had been some doubts about the amount of energy the 6kw turbine - funded by near-neighbours Scottish Power, the city council, and the Energy Saving Trust - would generate, given that Glasgow sits in a valley.
Yet it started whirring vigorously from the moment it was put up, and contributes the equivalent of 12 per cent of the school's electrical needs back to the national grid. Pupils are constantly aware of how much energy it is producing, thanks to a counter on the school's computer screens.
Inside the 280-pupil school, the first impression visitors make is on "the sense of space, of calmness," says head Liz Mahindru. Windows run right along the roof, and natural light pours in; the electric lights have barely been switched on since the school opened in March.
There is no air-conditioning. The building has been designed with ventilation chimneys and a multitude of windows, so air flows easily around the building. At the end of one corridor, a window - looking out to the turbine - is surrounded by Perspex, so pupils can see what fills the space behind the walls. Squint a bit, and you can make out some of the words in old newspapers. These are part of the 10 per cent of recycled materials used in construction - a percentage which is markedly above average, says Ms Cosgrove.
Elsewhere, the green aspirations are more obvious, with pillars made of telegraph poles holding up a balcony. Seven types of wood were used in construction, and the implicit link to the outdoors (not to mention the past - the site was once an orchard) is typical of the school's aim to blur the boundaries with the indoors.
Mrs Mahindru, who is "passionate" about outdoor play, says every classroom opens out to the playground and pupils go outdoors for all types of lessons. Even in heavy rain, balconies right around allow pupils to venture outside.
P6 pupil Amy Peoples is effusive when describing what lies beyond the school doors: "The thing I like most is the view over the allotments and the pitch. There's trees to climb and a big hedge. There's lots of places to sit and chat. I also find it fun to run up and down the hills - we've got lots of big hills".
All this is found in the first "natural play area", according to the Forestry Commission, at any school in the UK, designed largely by pupils with help from the commission, parent council and city council. It is a place that feels more like a woodland clearing than a sculpted playground, with tall grass, wooden stools, and so-called badger setts and foxholes (hiding pupils rather than nocturnal mammals). An amphitheatre and a ropebridge also beckon children outdoors.
There is another notable quality to the design, Ms Cosgrove explains. It was specifically not to be a "showpiece" project "plonked in the middle of nowhere", which would look dated within five years, but to fit in with and complement nearby housing and the neighbouring Our Lady of the Annunciation Primary.
Much is used by residents outwith the school day, and there is no fencing or security barrier around this area. That epitomises the effort to create a genuine community school, while deterring vandals. Physical barriers attract ne'er-do-wells by implying that there is something worthwhile behind them, says Ms Cosgrove.
The design of the school, however, has had the most profound impact on pupils and their appreciation of green issues. Mrs Mahindru knows staff have been preaching the same environmental messages for years, but the children have been far more inclined to recycle and switch off lights since they moved in.