Who's the fastest person in the world (apart from your line manager as soon as they get wind that you've got five minutes free)? Easy: Usain Bolt, averaging 23 miles an hour, which I've always found disappointingly slow. In my Hyundai i20 that feels like crawling.
Over a mile, the fastest man is Hicham El Guerrouj, who runs it in three minutes and 43 seconds. Over a marathon, it's Dennis Kimetto in two hours, two minutes and 57 seconds. Easy to Google, easy to understand.
But who's the best teacher in your school? What's the best school in your local area? Now there's a minefield. Yet we gaily forward-roll through this no-man's-land every day in education, every time we grade a lesson. Yes, I know we don't grade lessons any more - but we do. Despite the unambiguous "We don't grade lessons" smoke signals from Big Chief Wilshaw, every tribe still puffs back "Well, we do".
It's amazing how a scale as simple as 1-4 can blow the doors off the entire business of education, in the classroom and at school level.
Take 4: unsatisfactory, or "rubbish", as it really means. What does that look like? Most would agree on "unsafe, poor behaviour, no learning taking place". Most would even agree, at least in principle, that there should be a broad description of some kind of "satisfactory" setting (although what a jolly tango it caused when, in a truly Orwellian scene, satisfactory was no longer deemed to be satisfactory).
Above that, the picture starts to get murky. How do you know what good looks like? How do you know what outstanding means? An inspector once told me that he couldn't define outstanding, he just knew it when he saw it - it was "magical". I dismissed this starry-eyed Saruman as a witch doctor at the time, but there was truth in what he said.
Certifying excellence is mystical. How do you know when someone is a genius? How do you recognise when someone is better than you? There are so many styles of teaching that defining excellence becomes an exercise in prescription and prohibition.
Goodbye to all the crazy magicians and geniuses of the classroom, whose lightning refuses to be bottled. Damn them, of course, if no one passes or they can't keep a class safe. But the process of defining good or better is strangling the profession. How often have you seen a good teacher receive a heartless judgement of 3 from someone who can barely control a class but can follow an observation recipe sheet to the letter?
Bureaucracy is necessary to elevate a job into a profession, because bureaucracy is good at providing floor standards. What it isn't good at is promoting standards beyond that. Innovation is an atomic event. Why don't we bin the 1s and 2s and revert to a passfail standard for schools? Let professionals be professionals again. Let parents vote with their offspring if they deem the school to be good or outstanding, instead of leaving judgement to people who may be neither good nor outstanding.
And, for God's sake, can we stop grading lessons?
Tom Bennett teaches at the Jo Richardson Community School in Essex and is director of the ResearchED conference