The girls and boys in smart white blouses and shirts just keep on coming at Paisley Town Hall, as they troop onto the big stage to form a massed choir that would be the envy of any Welsh valley. It makes a sweet sound, when it starts to sing, but the music has an edgy rhythm and the lyric hits hard.
"Alcohol, not at all
Don't you drink that booze
Alcohol, not at all
If you do you'll lose."
A growing cause of ill-health and violence, alcohol is responsible for 40 per cent of accident and emergency admissions, rising to nearly three-quarters after midnight. Under-16s who drink today admit to twice the consumption of their peers 10 years ago.
But the sensible drinking message simply isn't getting through to young people, says Andrew Dickie, principal teacher of music at Paisley Grammar. "So we're taking a different approach, trying to get them on their own territory.
"There's no point in us standing up in personal and social education, saying: 'This is bad; don't do it.' That just doesn't work. We have to get the information to them, then they have to make the decisions themselves."
The medium chosen by Paisley Grammar and St Andrew's Academy to carry the message is a computer game backed up by a song, devised by groups of first-year pupils at the schools, who have been working together, funded by pound;35,000 from the Scottish Government, since last summer.
"They filled in application forms for three teams - English, music and graphics," says Mr Dickie. "We got loads of applications and we selected about 60 from the schools."
Teachers in music, English and technology at both schools worked with pupils on the project. A major benefit, he says, was the warmth that developed between groups of pupils at schools who would normally have few opportunities for friendly contact. "They got on exceptionally well."
For the success of the ambitious project - which grew out of an original idea for an alcohol-awareness board game - the pupils had to work well together. They were at the heart of the creativity and decision-making, although assistance was sought from the University of the West of Scotland and Kodetank, a computer games company.
"They did an incredible amount of work," says Mr Dickie. "We didn't have kids writing HTML - although some no doubt could have. But all the ideas for the type of game, the design of the cityscape, the activities and the look and feel came from them."
ThinknDrinkn is a mission game, in which participants try to reach a friend who has drunk too much and is sinking fast, across a city whose occupants are not always friendly and pose tricky questions about alcohol.
"It is stealth learning," says Mr Dickie. "We wanted to get across 15 key points about drink and its effects on young bodies and minds. So to get a high score, they need all that knowledge to get through the game fast. The great thing is that it's web-based and can be downloaded onto mobile phones."
The significance of this is revealed at the launch when he asks the audience of several hundred first-year pupils how many play games on their mobiles. What looks like every child's hand goes up - and no adult's.
ThinknDrinkn will be available on Glow, for use by any school in Scotland or beyond, and the entire approach could readily be adapted for other aspects of PSE, such as drugs and sex education, says Mr Dickie.
"We've tried standing up and lecturing young people about drink, drugs and cigarettes. It didn't work. If anything, it glamourised them. This is a different approach - peer-to-peer education, with all the concepts coming from the young people themselves.
"I'm amazed by how much we have all learnt and by the quality of what has been produced. Now we'll see how well it works."