It's only when the small group of third-years stand up at the end of the conversation that the rigours of life in the Celtic Youth Academy become apparent. Until then they'd been making light of their long days of football and education. But Jack Hendry's plastered forearm and Paul McLellan's crutches, to help him out till ligaments heal, give the game away - it takes character to do what these lads are doing.
"They've come here from different schools all round Scotland," explains Celtic's assistant welfare officer Bill Reside. "They're in at 7.30 every morning, so some have to be up at six. They get coaching, then lessons all day, then we pick them up and take them for more training and homework in the evening. It's pretty full-time. Getting their education right is so important for young footballers."
The partnership between St Ninian's and Celtic FC has taken the school to a second shortlist for the TES Schools Awards - for outstanding sporting initiative. Nearing the end of its first year, it is a partnership that is new to Scotland, says head Paul McLaughlin, but serves other top European clubs well. "The idea is that a better-educated, more-rounded young man will be well placed to cope with the exceptional demands on professional footballers," he says.
"The boys have settled well and are fully integrated into the life of the school. They've brought a vitality through their commitment to football and education . Although part of the Celtic project, they've quickly become St Ninian's pupils."
The best thing about the project is getting time to study as well as train, Jack says. "We do seven subjects instead of eight - which gives us a bit of time to work during the day - and we do homework in the evening. Before, I was travelling up to Celtic for training from Ayr and had no time to study at all. It was just football."
As an only child, Paul found staying away from his Dundee home tough at first, he says: "But hearing your mum and dad's voice on the phone at night helped. They're worried about you but happy that you're doing well. When I settled in, I realised I was developing better as a player, training every day. I used to just train with the squad on a Friday because I lived so far away.
"My education's come on as well, because if I miss anything there's always teachers here willing to help me. It's not about special treatment. They want you to be the same as everybody else. That's the whole point of us being here."
There is plenty of support from school and club, says Mr Reside. "But there's also an energy these guys bring. I wish I could bottle it and give it to some of the other young people I see as a youth worker in East Dunbartonshire. These boys have talent, but so do all young people. Some don't have the same focus."
That's something that comes partly from parents but mostly from yourself, says Keshan Nahar. "We're here to achieve something, to do well in education and football. It is self-motivation but the coaches drill it into you as well.
"I remember a meeting we had with Chris McCart, the head of youth at Celtic. He showed us a big list of things, and said we needed them all to be a good footballer. But it was more than that. You also needed them, he told us, if you wanted to be a good person."
The awards ceremony will be held at the Grosvenor House Hotel, London, on June 17.