I had forgotten what a startling, rare love song it is: a love song to a teacher, a guide and mentor and most beloved Sir. “How do you thank someone” sings the chanteuse “who has taken you from crayons to perfume?”

This teacher is not the victim of Pink-Floydian cries of “We don’t need no education!... No dark sarcasm in the classroom!...Teacher! Leave those kids alone!” but “a friend who taught me right from wrong, and weak from strong...”

Well, wow. What a great anthem for the end of another term, the sticky exhausted exam-soaked farewell to another school year. So prurient are we these days, so riveted by the possibility of head girls running off with maths masters and unbalanced supply teachers getting it on with priapic Year 11s, that we concentrate on preventing congress and elopement, and forget the pure and gentle old relationship, the platonic, grateful, sentimental affections that can arise in school life. To Sir, with Love. To Miss, in grateful memory. To the Best Head Ever. Sniff. Tears in the eyes.

Some friendships last forever: Tony Blair and `Eric Anderson, or indeed my friend Emily and the history teacher of 1965 who was the first adult to give her intellectual confidence, and who she still visits monthly in his nursing home - “Not for his sake, either. For mine”. Mostly, though, I think that for my generation it has been rare to forge a post-school, equal-terms friendship with a former teacher. In the 1960s the glass walls still stretched from floor to ceiling, the generation gap seemed unbridgeable even between 18 and 25, the decorum of school life hung between us as a great mournful gulf. Perhaps that’s why there’s such sentiment in “To Sir with Love” - because in that era, in Don Black’s era and mine, it wasn’t really likely to be a lifetime friendship, even if you lived within the same neighbourhood. It’s always the impossible relationships which shine the brightest on the misty horizon: just as it is always the remote, half-remembered awful teachers who become sacred monsters in the distorting glass of the Friends Reunited website.

I think, though, that things have changed. I suspect that the present generation of school-leavers will be more likely to extend a school friendship with a teacher into the rest of life, with ease. And not in an erotic way either - wash your mouth out you dirty beasts! I mean that real friendship can flower more readily in this more informal age, particularly when education extends into the sixth form. My children’s generation seem more natural, more joshing, more jokey with their teachers as they reach the end of school life.

University students go back and have a drink with the former Sir or Miss, pass on the gossip and the handy hints for getting the next generation onto the right course. Gap year postcards arrive not only for parents but for favoured teachers, and are pinned up in the staffroom. Teachers climb down more readily from their professional dignity, and go to the pub with former pupils, and gradually the sense of daring in the pupil and of awkward patronage in the teacher can subside, and staffroom gossip can even be shared on an adult-to-adult basis, and guffaws exchanged over bygone detentions and sparring-matches. “Remember that school trip when we couldn’t find Kevin anywhere and he was asleep on the bog in the National Theatre? Remember prize day when the Lord Lieutenant was so boring Miss Runcible fell off her chair because she’d been up all night doing reports?”

I hope it is getting easier. I hope the Sirs and Misses of today, who are after all only human beings needing affection as much as any of us, are becoming friends with ex-pupils. It would be a nice reflection on which to end the school year.

Have a good summer. Be sure to take an ex-pupil to the pub. Some of them can even drive you home, these days. Perhaps there’ll be karaoke. Perhaps he, or she, will sing “To Sir, with Love”. One can dream.