So, on the morning of the leavers’ assembly we went into action. The revision of the previous week had been pushed aside while we painted old bed sheets on a friend’s kitchen floor. We entered the sixth-form block by the back door and, as two of us dropped the fishing lines from a classroom above the main entrance, a third on the ground hooked on the banner and watched as it was hauled into the air. It billowed brilliantly in the May rain for a minute, before a gust caught it like a sail and snapped the line. We grabbed it, and hung it instead from the school railings.

Harrogate Grammar Upper VI Leavers’ Assembly had, for the cars slowing down to watch, become “Otley Road Lunatic Asylum Open Day”. Puerile exhibitionism? Well, kinda. But how could we resist?

We weren’t alone, at least. The fish counter at Asda had been visited by some of our leavers that morning, and by 10.30am a party-size seafood platter and a dozen haddock had been hidden in ceilings around school. A little cruel; with July hitting 30 degrees, flowers would have been a more fragrant way to say goodbye. Meanwhile, an unplanned “room change” notice had been printed out and stuck to every classroom door in school. While we filed in to assembly, a carnival of confusion erupted on the corridors with classes sent to the same, and sometimes non-existent, rooms.

And so began the assembly. Seven years is a long time to stay anywhere when you’re a teenager. Those walls, and the mentality within them, become a part of your identity. Yet, though we’d sat in the hall before those teachers so often, something had changed. They’d put together a slide show of themselves leaving their own sixth forms. Some had barely changed; some, as our baffled jaws bounced off the floor, were pretty hot; and some, as the commentary put it, looked like members of the BNP.

The rigid pupil-teacher roles we’d grown up around crumbled then to something more ambiguous, nudging towards being equals. We were just like you once, the PowerPoint faces said. But a warning too: leaving school means growing up, and one day you’ll be like us, with bald patches and mortgages. Cripes.

We headed to town to drink. It was a halfway celebration; school behind us, but revision and exams in front. In the preceding week we’d all bought leavers’ hoodies, leaving us a tribe 200-strong in black, our names in red across the back. They held us together in Wetherspoon’s, picked out against the blue and grey of those of our rival schools. But something between us had disappeared. For seven years we’d been bound by a common future, tied, whatever we did, by the next lesson, the next school trip. Now that certainty was gone, and the next time we’d meet it would just be as friends.

We toasted, waving signs prised on the way out from the toilet doors, to never losing touch. As we each made a hundred plans for our new-found lives alone, how many of us believed it? Hard to say.

And then I went home. And that was the end of school.

Matthew Holehouse has just left Harrogate grammar school. His Teen spirit column continues through the summer. Email: mattholehouse@hotmail.com