You know who deserves a medal? Supply teachers. They’re one of the most marginalised groups in the school ecosystem, forever wandering around schools waving their wee bells and calling out “Unsure! Unsure!” so everyone knows they’re not real teachers and you don’t have to listen to them.

I’m being sarcastic, of course. We like to tell rookies that they’re not student teachers but full-throated bona fide teachers who happen to be new. It’s the same with supply teachers. They’re not pretend teachers; they qualified like you and me. They aren’t a meat substitute; they’re Wagyu steak fillets.

But you wouldn’t believe it at some schools. The supply teacher bowls in looking for a morsel of orientation and often gets pointed towards a noisy corridor. “See that?” they are told. “Teach it.” If they’re lucky, they get a lesson plan. If they’re really lucky, they get a decent lesson, a seating plan and the name of a ranking officer. It’s rare, though, because some schools - too many - see supply teachers as a sticking plaster; a pair of tights pretending to be a fan belt until you get home. This leads to expectations that are painfully, perilously low. “Survive” we tell them by our actions, and our inactions. “Endure.”

The kids spot this in a heartbeat. From the second the supply walks up the corridor and the first likely lad beats a happy tattoo (“Supply! Supply!”) to his colleagues, the covering teacher can tell if the next hour is going to be a lesson or a gauntlet. The students know how the school views supply lessons just as well as we do - better, in fact, because they aren’t glued to the pieties of our public discourse. “A supply lesson is still a lesson,” we tell them seriously, while chucking supply teachers in at the deep end with no more than a scrap of paper that has “The kids know what to do”, “Revise for the test next week”, “Work on coursework” or “Draw your hand” written on it. I’m not making any of this up - these are all lessons I have been given to cover. If we don’t care about what the kids do when we’re away, why should the kids?

Another thing: supply teachers are often an interesting breed. Legend has it that they’re in supply because they couldn’t get proper jobs; that they’re tired out or eccentric. Maybe that’s true for some. I’ve known broken arrows, sure. But I’ve also met travelling geniuses: Gandalfs, bards and lion tamers, self-sufficient as a one-man band, who can pull tricks from their sleeves like magicians’ doves. Some can teach on their feet, with nothing but a good idea, a voice and nerves of adamantium. Imagine what they could do with a decent lesson.

You can tell a restaurant’s kitchen hygiene from the state of its toilets; supply teachers are a similar test of a school’s health. Walk past a supply lesson: if the kids are facing the right way and making a decent fist of it, the school has a pulse and a heart. If they’re re-enacting Gallipoli, the school hasn’t instilled good habits that survive the absence of the regular guard. To understand what a school is really like, ask a supply teacher. They know.

Tom Bennett teaches at the Jo Richardson Community School in Essex and is director of the ResearchED conference