Stephen Byers, the school standards minister, announced this week that a school's GCSE pass rate must include pupils who have been permanently excluded for up to two years before the exam. The aim is to remove pressure to ditch pupils likely to perform badly.
He said: "There is concern that some schools might be excluding pupils in order to improve the school's position. This damages the children concerned and deceives parents and the public."
But the National Association of School Masters Union of Women Teachers reacted critically.
"Overall results will be far worse affected by continuing to tolerate disruptive pupils," said general secretary Nigel de Gruchy.
"This grubby move serves only to illustrate that politicians and league tables need reforming, not the desire of schools to protect the majority of pupils against the disruptive behaviour of the few."