The memory was intensified, I suppose, because my own children are getting to that stage. One has left school and the other will a year from now. But whatever is causing it, it is powerful: long days, long grass, relief at the lifting of long years of pressure to revise and remember. I can feel again now the high spirits, the extravagant hopes for the new life and the occasional sickening plunge of self-doubt: "Hell, this is it, this is real. I'm not a school kid any more..."
On one of those last few days of term, three of us - and we still keep in touch now - sat on a grassy bank overlooking the railway line at the bottom of town, sharing a bottle of cider and wondering where we would be in a year, 10 years, 30 years. We were boarders, but elsewhere on that blessed embankment sat girls and boys from the grammar schools in town, doing exactly the same as us.
And, what is more, both they and we would be expected back for the end-of-term assembly and the final moments with our teachers and peers. The British system being what it is, there was no graduation - by the time any of us knew our A-level results we would be scattered. But we all finished the school term.
That was how it was: and how the odd, dreamlike time of transition was granted. We each found our own way of passing it, although altruism was suggested. I spent hours down in the school basement confronting the bin bags full of milk bottle tops we had collected "for the blind". The recycling charity had suddenly closed down so, until the school could find another one, it had got stuck with a mountain of cheesy-smelling aluminium foil. It was starting to stink out the pottery room, that hot summer, so a couple of friends and I offered to wash the bottle tops. Our efforts were more or less disastrous - amusing though it is to pour hundreds of tinkling whiffy bottle tops into the craftroom sink and shoot hot water at them, it had little effect - but it kept us busy.
Then I wandered off to join a favourite teacher who was struggling with costumes for the junior school play, and offered to read aloud to her. Her tastes were eclectic and thus it was that Sister O'Leary and I got through the whole of George MacDonald's Phantastes, in the gap between the end of examinations and the beginning of real life.
All this came back to me, with the power of a long-forgotten riff from Manfred Mann. And today, among the 18-year-olds, and even 16-year-old leavers, there is evidence of the same kind of time being had: fetes and fun, days prepared, spirited attempts made to wade in and help at the local playgroup. But mostly, it seems to be dull diaspora.
Even as many schools - state and independent, and even boarding - have taken to copping out of their responsibilities by declaring "study leave" back in April and sending the examinees home to fret unsupported, so also have they rejected the old idea of hanging on to the very end of term.
Every year, we get the same news stories about institutions so unconfident in the loyalty and sense of their leavers that they declare an early end-of-term and throw them out without warning, or simply inform parents that once the last exam has been sat, their child is no longer welcome on the premises.
I suppose it is tied up with the fact that 18 is entry to legal adulthood and I dare say there is something to be said for abolishing the cultures of suspicious supervision and old-school sentimentality.
Good luck to the kids who use the time selling ice creams or working on tills to save up money for university. And well, some respect to the cheery hedonists who take off immediately with the only friends they care about for a prolonged gap-year debauch.
But when I smell the hot grass, or hum a bar or two of Doo wah diddy diddy as I see the few remaining end-of-termers hugging and sniffing and spraying one another with fizz on the last day, the pang of nostalgia is strong.
There are not many points in a modern life when time stands still and nothing is urgent and one phase is over and another not begun. That interlude at the end of school was one of them: you were not adult and not a child, not busy but not bored, uncertain of your future but not scared. You floated free. It was good.