Labels are easy to overlook. Fat free, reduced sugar, a third extra, eight out of 10 cats, the nation's favourite... Labels are so ubiquitous that their pleading rarely registers. When they are applied to people, however, it's different.
Excellent cook, dedicated mother, hopeless drunk, inspirational leader, dodgy accountant - those descriptions tend to stick, especially if they are widely disseminated. How about "least effective" maths teacher? If a newspaper named you as one of the least effective teachers in your area, how would you react?
A few years ago, the Los Angeles Times decided to rank individual teachers according to the progress made by their students. The rankings were necessary, it claimed, because there were no other performance measures. Assessing progress rather than achievement was fair because it measured the value added by a teacher rather than the prior attainment of the child. It was superficially egalitarian: teachers of poor children weren't penalised because they taught in poor schools that tended to perform badly; teachers in wealthy neighbourhoods couldn't automatically claim the credit for the top grades their students usually achieved. It all seemed so logical - until it was applied to actual people.
Rigoberto Ruelas was one of the "least effective" maths teachers in the city, according to the Los Angeles Times. A few days after it published its verdict, Mr Ruelas was found dead. He had committed suicide (pages 28-32). His family said his poor rating had driven him to despair. His colleagues were outraged. Thousands protested.
Today the paper remains unrepentant; it is planning to publish fresh ratings. The New York Times appears untroubled, too. It ranked 18,000 teachers in a similar league last year. The US Secretary of Education backs them, urging teachers to man up: "The truth is always hard to swallow, but it can only make us better, stronger and smarter." Politicians know these things.
These august endorsements, however, should not blind us to other sobering truths: the data are unreliable, the benefits are unknown and the human costs are all too obvious.
The Los Angeles Times, with breathtaking insensitivity, admits that "confidence in these figures varies" and that some of the data were a bit "squishy". Others are less coy. The data were "demonstrably inadequate", according to one research team. An "absolutely terrifying" and needless public exercise, said another academic. Even if the data were accurate, he added, how could it possibly improve teaching? Ludicrously, teachers of gifted students score poorly because progression is limited. An A-grade student cannot be upgraded.
Thankfully, there are no signs - yet - of teacher league tables being adopted outside the US. They were allowed to sprout there because the country lacks other accountability measures. If you never felt grateful for Ofsted before, start now.
There is another lesson to be learned. No country can improve its education if it shames and blames teachers on a regular basis. All the international studies - the ones with respectable data - agree that the best-performing systems esteem their teachers highly. Public humiliation doesn't seem to feature in any of them. And neither do undeserved epitaphs that sign off a person as "least effective".