They don't just do it on a nationwide political level. OFSTED compare a school to "similar schools" to make decisions on whether there's a performance issue. It's bad enough comparing one year's results to another, as you can get a different incoming level of education each year, but to compare with another school based on the fact that eight years ago, you got a similar set of results to them is just ridiculous.
Again agreed. It's not the OFSTED judgements I treat with disdain, but the sages at institutions like the OECD whose research is the used by octogenarian press barons to bring back learning sines and cosines by rote.
World education rankings: which country does best at reading, maths and science? | News | guardian.co.uk