Offering students sweets and vouchers is all well and good. But if we don't make them love a sense of achievement in its own right, all we're really teaching them is self-interest

Last summer I spent three terms' hard-earned savings on flights to Mexico, justifying the eye-watering cost with a promise to live frugally throughout the trip. I spent a few weeks – and minimal cash – searching out natural pools and jumping into them. It was great.

At a particularly spectacular one, I was joined by a family of two jovial parents and two tremendously grumpy teenagers. The mother and I exchanged a knowing laugh as her po-faced offspring point-blank refused to jump 15 feet into the warm, turquoise water below. Then her husband offered them $20 (£12) each to do it. Her son instantly switched to negotiation: "I'll go twice for 30 bucks." The poor woman looked mortified.

I know how she feels. I effectively bribe students in my class to bother about their work. It's awful, I know, but when my charges are getting a bag of Haribo in science and a mini Mars bar in maths, a heartfelt "excellent work" from me is more of a slap in the face than a pat on the back. Consequently, my department could keep the south London lollipop industry single-handedly afloat.

Management are in on the act too. When we handed responsibility for after-school revision sessions over to the senior leadership team, we were chuffed, if a little confused, to see attendance soar to almost 100%. Then we saw 30 greasy pizza boxes congealing outside the hall. Give a man a fish and he'll eat for day, give a year 11 three slices of meat lovers special and he'll self-assess a mock exam, create 15 revision cards and complete your post-it plenary without a word of complaint.

This is all well and good in the short term – lets look at how focused they are, marvel at the colour-coded, group-created poster about answering question three – but what are we really teaching them? The irony of analysing Animal Farm in return for individual material gain may be lost on my pupils, but the effect of a what's-in-it-for-me culture is certainly going to stick in their brains if it's reinforced regularly at school.

Our pound-shop fun packs are the thin end of the wedge. Parents are apparently happy to dole out cold, hard cash for academic success. I don't mean the traditional tenner in a card on GCSE results day; there's a steady flow of currency for successes ranging from an A in an essay (£20) to, in the case of one of my year 10 pupils, staying out of late detention for a week (£50).

What's more, this is a message we repeatedly reinforce in attendance assemblies. Why should our pupils come to school every day? For the intrinsic enjoyment of knowledge and development of their characters? Of course. Well, that and a place in the draw for a £100 JD Sports token.

There's a pernicious Powerpoint presentation about future earnings that's been doing the rounds in PSHE for years. It advises its beholders that to be in the top bracket of earners, you need to complete your GCSEs and get yourself a university degree.

But isn't that backwards? When I was pulling all-nighters to finish my dissertation, it wasn't the warm glow of earning £15,000 a year more than the girl I sat next to in form time that kept me going. When I battled through Paradise Lost, it wasn't even because I enjoyed it (no-one did). I liked the feeling of being befuddled by Milton. And I loved the feeling of finally getting it. To put it simply, I enjoyed understanding stuff.

Ultimately, we're setting a grim precedent; the repercussions of raising a generation to be driven solely by rewards will be felt far beyond the school gates. Why do something for nothing if the only measure of success is material? Unless we can internalise the incentive to learn – to make our students love that sense of achievement in its own right – we're teaching self-interest and short-termism above all else.

And with the promise of performance-related pay looming over us all, isn't this what we're being trained to think too? Why come to work every day? For the intrinsic enjoyment of teaching and developing young characters? Of course. Well, that and an extra five grand a year if you can get them to exceed their target grades.

This week's Secret Teacher works at an academy in south west London.

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