May is the saddest month. Actually, strike that. It does have a positive side. It’s sad because the sixth-formers are leaving for good, but happy because when the exam classes disappear, my timetable will be lighter than a bag of Maltesers.

This theoretically frees up enough time to spring-clean my classroom, empty the recycling bin and round up the loose drawing pins skittering about in my drawers. In reality, of course, none of this will happen, because as soon as management have sniffed out the fact that I have time on my hands, I’ll be drafted into the latest black-hole whole-school initiative and all my spare seconds will be sucked into the void.

Saying goodbye to students is hard, particularly as the claustrophobia of exam prep makes the relationship between teacher and student so intense. No matter how many times you do it, preparing a teenager for their A-levels is traumatic because, unlike other exams, so much rides on the results. These are their X Factor finals; everything else was just yodelling in the bath. And like anxious mothers weighing newborns to see how much they’ve gained, we microscopically measure students’ timed essays and pin the blame on our own bad teaching when they make no progress. As indeed do the students, conveniently overlooking the fact that six hours a night on Facebook, a part-time job at Boots and a predilection for Red Bull are hardly prime determinants of optimum exam success.

Nevertheless, these last few weeks are emotionally charged. That’s why the “last lesson” is such a cathartic affair. It feels like a cross between the Last Supper (except with Quality Street instead of bread and wine) and that scene in Toy Story 3 when Andy goes off to college and leaves his toys behind. And it takes teachers a while to recover, because no matter how much we look forward to working with the new kids, we still have the names of the old ones etched on our souls. Especially that one who complained about us to the assistant headteacher.

But the best thing about saying goodbye is that finally you find out how much you mean to your students. Their cards may be syrupy, sentimentalised works of fiction, but for an A-level teacher this is a performance measure that knocks the rest into a cocked hat. What’s a 20-minute summation from a stranger in a black suit compared with the final appraisals of your students? It doesn’t matter that they’ve written “You’re simply the best” to 10 other teachers. Or spelled your name wrong. Or spilled Diet Coke on the card. The fact that they took the time to tell you how they feel makes it all worthwhile.

It’s the teaching equivalent of those not-a-dry-eye-in-the-house cinematic moments. We know our students value what we do. But we know it even more when we get a bunch of flowers, a box of chocolates and a gift card for House of Fraser.

Beverley Briggs is a secondary school teacher from County Durham