Our school song at Ecclesfield grammar was the same as Harrow's: "Forty years on when afar and asunder, parted are those who are singing today, when you look back and forgetfully wonder, what you were like in your work and your play..."
It's not a bad song, but in 40 years we'll not have forgotten what school was like. Schooldays, like service in the armed forces, stick in the mind when other, later memories fade.
Why? Satnam Singh Chana, 12 years out of Sidney Stringer comprehensive in Coventry, remembers "the Hexagon, where we used to hang out, or the bridge where we used to meet". Dig a little deeper, though, and it comes down to people and friendship. For Satnam Singh the place remains important because he still lives nearby - but its true role now is as a reminder of a happy time with friends. "We had a blast," he says. "I'd go back tomorrow. I can't understand people who say they didn't enjoy their schooldays."
Satnam Singh, now 28, organised a reunion last year in a local pub (few reunions seem to happen in schools themselves). Of 123 people in his year group, he contacted 80, and 50 turned up on the night. "We had a few beers," he recalls, "and a lot of chit-chat about what we were all doing. We had a mix of people, Asian, black, white, and some Muslim girls who aren't usually allowed out at night. That was good."
None of them, he says, had changed much. "Some had families, some were still into clubbing, but the funny thing is it was seriously like being back in school."
Given that this was a group of people in the midst of career-building, inevitably some networking went on. "I was a purchasing manager at the time," says Satnam Singh, "and I was able to pass on a bit of business."
Coventry comprehensives seem to generate a nostalgia that some more venerable institutions would envy. Binley Park School, for instance, opened in 1959, closed in 1990 and has now vanished beneath a business park. Nevertheless, there's a Binley Park tribute website so filled with photographs, and the memories of former pupils, that it has become a virtual-reality reunion in itself.
Neil Grantham, who runs the website, left Binley Park in 1978. It was, he says, a good place to be educated. "People seem to remember it with affection. I think the fact that the school got knocked own has a lot to do with it," he says.
Eva Cheung, from 1987, sees the website as a way of keeping in touch with old friends, some of whom she now plans to meet. "It's curiosity more than anything," she says. "It's just got the better of us. Will I be disappointed? I don't think so; we've all got to be better now than we were at 16."
What about people who were unhappy at school? Even their feelings can be more complicated than you might think. Richard Smith (not his real name), 29 and a self-employed painter and decorator, has a particular reason for attending reunions. "I was bullied at school, all the way through. So if I did go back it would be to say 'Look, I've ot my own business - I'm not as useless as you lot thought I was'."
Perhaps the best summary of the reasons people revisit their schooldays comes from businessman Fred Link, of Kansas City, Missouri. In the United States, each high school class has a yearbook and class president. Fred does the honours for his 500-strong class of 1969 at Harry S Truman high school. The class has now met at 10, 20, 25 and 30 years on, usually in a hotel at a weekend.
Motives for attending are many and varied. "Some who weren't seen as very attractive at school might come back to show themselves off," says Mr Link. "Others will go to anything with a party attached to it. Then there are people who want to talk about their success."
Later on they'll want to talk about their children's success and eventually they'll claim "grandchildren bragging rights", he says.
Most people bring partners (always an issue for reunion organisers). "Those who don't," he says, "may be on the prowl for their old high-school sweethearts."
He feels that the typical reunion person is the one who was quite successful at school. "They usually had a lot of friends and they come curious to know what they are like now."
That's reflected in the feelings of today's young leavers. Zoe, not long out of a Warwickshire comprehensive, says: "It's too soon. Maybe I'd go later on, just to be nosy. It's difficult to say."
Alex, a Coventry sixth-former, is very keen on the idea - but not yet. "Oh yes, I'd be up for that," he says. "Maybe five years on when we've all settled down a bit."
Some of the best reunions are those where the people haven't met for many years. Tom Whitehouse is one of a group who ran two reunions - in 1998 and 1999 - of the 1948 Form Five Alpha at Blackpool grammar school. "I had these big name-tags waiting by the door," he says. "People thought they wouldn't be necessary, but less than half were instantly recognisable. One person I recall as being sports-mad at school had become a big consultant in a London hospital. He'd swollen to fill the role - grey hair, half-moon spectacles, not a bit like the boy we knew." Mr Whitehouse talks with nostalgia and affection of a school where, he says, "the cream of the cream were taught by the cream of the cream".
Those "deep-time" reunions - 30-years plus - bring out the sense that you are revisiting your former self, with all the accompanying emotions about what has happened to the years between.
About five years ago I went to a reunion of 27 of my 30 peers in Ecclesfield's class of 1953. I proposed a toast, and as I spoke and looked out at the smiling faces of my old friends, I tried to describe my feelings about the joys, surprises and sometimes tragedies that had lain unseen ahead of us, and the quietly thankful sense that we'd made it through to the point where we could meet with love and laughter in late middle age.
"To us - then, and now," I said. It was quite a moment.
The internet is a rich source of help and information on reunions. Search by school name, or by 'reunion' or 'find school friends'. Sites available include www.school-friends.co.uk, with many links to schools, and messages from people wanting to make contact. The Binley Park Tribute site is at www.binley-park.org.uk.