It was a moment instantly burnt into the skin of my memory. A high school history teacher who planted her hands on the edge of my desk, leaned her face towards mine and said with a strange kind of anger: "There is nothing new under the sun, Julia. No thought, no idea – they have all been said before."
We had been arguing about something that escapes me now, an ancient skirmish or far-off war and I had pressed the point, to her obvious irritation. I still remember the flash of fury I felt, at being told at the age of 16, that I would never have a new thought, that all was inherited, all tracks worn, all roads trod; as though human thought was an exercise in mass, if inadvertent plagiarism of previous generations.
Don't dare, don't dream, it's all been done before. I now understand it as a central tenet of history – that human folly, striving, madness, triumph, repeats itself – but it is so often in infinitely new ways. And surely every kid should only ever be told to dare to do and be more.
When we talk of the teachers who shaped us – and many have last week thanks to Thursday's World Teachers' Day – we most often speak of those who taught us to roam, who stepped out of curriculums and dismantled boxes of conventional thinking, who saw something in us.
Who didn't contain us, but released us.
We don't think as often of those who set our jaws in defiance by telling us what we could not do. My friend Bernard Zuel, legendary music critic, told me his tech drawing teacher told his "bunch of arty type" friends that they were "pseudo intellectuals who wouldn't amount to anything". He says: "None have forgotten."
Talented broadcaster Hamish Macdonald – who in the past few days alone has hosted The Drum's rolling coverage of the Las Vegas shooting and RN Breakfast, was told by his journalism lecturer that he would "never have a future as a broadcaster" after doing his first air check.
A high school physics teacher told Professor Michael Biercuk, a quantum physicist with a PhD from Harvard, that he couldn't do well on his final exam. The teacher could not have been more wrong.
For every Miss Honey (Matilda) and Professor John Keating (Dead Poets Society) and Dumbledore there is a Snape, or someone who did not get us, who told us to simply perform, to shrink, not expand.
But watching Twitter swarm with stories of great teachers – famously underpaid, overworked and underappreciated – was warming. Teachers who tell people to be fearless, teach them how to harness the angst and storm of adolescence or intelligence and encourage to question the world, not only themselves.
I will always be grateful to my second grade teacher, who let me spend hours writing poems and told us to lie under trees and describe what we see. My English teacher Betty Curran who loved ideas and didn't care for rules and my history teacher Mrs Vacchini, whose passion for history permanently infected me. Now, I am watching it with my daughter – her teacher this year has recognised depth in her and she has bloomed as a consequence.
But despite the fact that Twitter lit up with feel-good stories and the hashtag #worldteachersday #thankateacher was trending, it's sobering to reflect on how little we really do appreciate our teachers.
The Global Teacher Status Index – which surveyed views of teachers in 21 countries – found the only country where teachers are considered as important as doctors is China. The author of the index says attitudes to teachers are shaped by cultural values.
According to the Organisation for Economic Co-operation and Development, between 2005 and 2015, teachers' wages dropped in one-third of countries. Yes, dropped, in real terms. In England it was 10 per cent, in Greece it was almost a third.
Teachers, who seed every other profession, who mark every life. You'd hope we'd put our money where our tweets are.
Julia Baird hosts The Drum.