IN Jonathan Swift's poem A Beautiful Young Nymph Going to Bed, he describes "Corinna, Pride of Drury Lane" as she undresses at night. When she awakes, without her mouse-fur eyebrows, false teeth and the rags that prop up her "flabby dugs", it's not a pretty sight: "Corinna in the morning dizen'dWho sees will spew; who smells, be poison'd."
I'm reminded of this because the other day a colleague popped her head round my door and caught me - pedagogically - in a similar state of undress. The lesson hadn't gone to plan. The kids were engaged in multifarious off-task activities, such as chopping up erasers, checking their mobiles or staring catatonically at the floor.
Only one pair were discussing their work. At least I thought they were; when I drew nearer I discovered that the topic of their lively debate was not Hardy's use of metaphor but whether they had maths or art after break. As my colleague withdrew, I felt exposed.
Teaching reputations are built on sand. All it takes is one poor lesson observation to catapult you from being the toast of the team to being some kind of canker-ridden classroom Corinna, simultaneously reviled by the senior leadership team and pitied by your peers. That's why we beg to be observed with sixth-formers or the eager beavers in Year 7.
If someone suggests watching you with a more challenging class, the customary excuses are reeled out: it clashes with a hospital appointment or doesn't support your performance management targets (you should always set your targets on stretch and challenge or raising sixth-form attainment for this reason). All of us avoid challenging classes because, from the observer's point of view, it's hard to see real progress being made. It's difficult to attract a good judgement when the start of your lesson is marked by a human wind farm of flailing arms as kids demand to go to the toilet and the rest is given over to tribal indignation because last week you let Daniel Ramsbotham go and he wasn't even bursting.
But the choice is out of your hands when there's an Ofsted inspection. And your previous professional standing won't do you any favours either. Last year, in a different school, I was observed teaching a top set of Year 11s and the lesson was deemed outstanding. In reality, it was a group of academic, middle-class kids who'd been hard-wired to succeed; the judgement had more to do with their leafy postcode than my professional practice.
In my new school, however, the prospect of inspection is more daunting. Progress for one of my trickier charges - a boy with a reading age lower than his shoe size - might be simply agreeing to read aloud from a book rather than hurling it on the floor.
But, just as the ambitious parents of my previous class were collaborators in their success, the same government that sends in the inspectors has, by dint of closing libraries and Sure Start Centres, co-parented this boy's failure to read. When you remove the social scaffolding for literacy success, the result is as shocking as Corinna without corsets.
Beverley Briggs is a secondary school teacher from County Durham.