My conscience won't let me sleep. Returning from a career break in a limited job market, I decided that, if teaching was "just a job", as my non-teaching partner kept assuring me, it wouldn't really matter where I went.
Ignoring the internal cries of "Shame!" I accepted a job at a grammar school, in contradiction to every view I have ever held on education and schooling.
It's a serious bypass of my politics and principles. Never mind being anti-grammar, I don't even agree with setting. Both systems privilege those with supportive families and a consequently good work ethic. More worryingly, both disadvantage those who are already struggling with more than their fair share of disadvantage at home, by jamming an iron ceiling on their already low expectations.
Nonetheless, I convinced myself it would be a professional adventure - a chance to challenge my prejudices - and it's state run, so technically I wasn't straying entirely from the path of righteousness.
I underestimated the culture shock. With every passing day, my sense of social injustice grows sharper and scratches more insistently at my guilty left-wing soul.
Technically, these students are selected by ability, but the roll call of Sebastians and Sophias tells a different story.
State grammars are no longer the fabled places where poor boys could be lifted from humble roots and begin the hallowed path to Oxbridge and the Tory party. No. These boys and girls are here largely thanks to sharp-elbowed, deep-pocketed parents shelling out for private tuition or even prep schools to ensure the holy grail of an 11-plus pass.
They are delightful pupils. They love their school; they work with energy and enthusiasm; they don't even groan when I set homework. They hang on every word with an attention bordering on admiration.
No wonder the teachers seem calmer and more contented than any others I have ever known. When I reflect on how we thrash ourselves at comprehensives in the pursuit of results - how, crippled by self-doubt and media carping, we constantly ask ourselves what we can do to improve - I am floored to realise that, here, learning is taken for granted.
There's no anguish about plenaries or objectives. There's a liberty, an enjoyment, a self-confidence among staff, and above all, a belief throughout the school community (students, parents, teachers) that the hard work has to come from the pupils.
And come it certainly does. These children, nurtured and fretted over by well-heeled parents, care deeply about their own education and are unashamedly keen to succeed. Obviously, comprehensives have children like this, but in the grammar school there are almost no exceptions. They achieve outstanding results, but they are not, as far as I can see, outlandishly able. What they are is supremely, extraordinarily motivated. And supremely, extraordinarily middle class.
At night, I think about how to bottle this magic motivation and take it back to Comprehensive Land, because, with that on our side, we wouldn't need to keep beating ourselves up: we could make every child a success story. But, without the gilded socio-economic background to shape students' aspirations, the parents who relentlessly prize education, or the promise that society offers them equality of opportunity when they leave school, I might just as well be dreaming.
The writer is a teacher at a grammar school in Kent.