I was on my way to the photocopier when I took the call. As soon as I answered I knew something was wrong. “Mum’s being rushed to hospital - can you meet me there?” Once, a message like this from my husband would have had me dashing straight for the door. But 10 years in teaching has skewed my moral compass; it now drifts towards educational exigency rather than doing the right thing.

I considered my options. On the one hand, my mother-in-law was dying; on the other, I had five lessons the next day and nothing prepared. Could I delay for a few minutes? Because as much as I love my 80-year-old mother-in-law (and I do, enormously), the thought of facing my Year 11 class armed with only a whiteboard marker and a nervous grin filled me with despair.

Work won. I sneaked off to the photocopier and prayed she would outlive three sets of 30 sheets. Fortunately she did. But the incident made me take a good look at myself in the moral mirror.

A few weeks later, my morning drive to work was blocked by an accident. When I heard myself asking the policeman “How long will this road be closed?” rather than “Is anyone hurt?”, I knew it was time to quit. I resigned the next day. My decaying personality may have been the result of a debilitating lack of sleep, unrealistic data demands or spending too long on Crossy Road, but none of these excused what I’d become. I was a pedagogical Dorian Gray, all cardigan-ed compassion on the outside as my soul rotted away in a dark attic.

The pressure to perform well in school can make us into monsters. Take the popularity of the IGCSE, which for a little while was the back-alley rat-run to accountability success. With 60 per cent of the marks based on teacher-assisted coursework - as opposed to 40 per cent teacher-free, oh-my-God-they’ve-even-spelt-Steinbeck-wrong-in-the-title controlled assessment - heads of English departments signed up in droves. Even though, to ratify it, we had to short-change the kids with “literature-lite” - a curriculum containing as much literary merit as a Ukip tweet. In my darker moments, I fear that everyone is doing the same. Doctors who were taught “appendectomy-lite” are handing out Gaviscon to people with failing organs, while dentists who studied “anaesthesia-lite” are drilling into unfrozen gums.

It wasn’t easy to hand in my notice. Teachers are the most amazing people I know, but the thought of what’s happening in my attic means I’ve got to go. I’d love to say that I am thrilled with the decision, that I feel like Steve McQueen flying over the fence in The Great Escape, but in reality I feel a bit flat. I worry that, just as amputees still feel their missing legs, my mind will jerk to the clockwork rhythms of the school day for a while to come.

I love education too much to leave it entirely. Like many before me, I’m going down the gamekeeper-turned-poacher route of becoming a consultant. The best thing about my new role is that I get to carry on working with stoical, life-affirming, gutsy people like you but without giving Satan first dibs on my soul. At least, not in the first week.

Beverley Briggs was a secondary school teacher in County Durham