Leading article: Teachers are right... class sizes matter

The mood of militancy emanating from the National Union of Teachers' conference this Easter means that schools in England and Wales may face the first national teachers' strike for 22 years. So what's new, you might ask. There are often strike calls at teachers' conferences that never come to anything. This year, though, the mood is different, and the militancy comes from the top, not from rank and file activists trying to overturn more moderate leadership.

There are two issues driving the calls for industrial action – pay and class sizes. On both, the Government can fairly claim to have improved the situation in its early years. But on both they can now be accused of backsliding.

Pay is the most immediate issue with a one-day national stoppage planned for next month, followed by a rolling programme of further action through the summer. Teachers argue that the profession is again facing difficulties retaining staff, with half of all new recruits leaving after three years.

But it is on class sizes that the union detects that ministerial good intentions have gone into reverse. One of Tony Blair's five key promises (indeed, his only education promise among them) was a legal limit of 30 on class sizes for five to seven-year-olds. He delivered that ahead of time, but there was a widespread assumption that it would be just the first step towards smaller classes throughout the system. Teachers, and many parents, were happy that the Government seemed to share their view that small classes were a good thing in themselves.

Quite soon, though, it became clear there would be no further effort to reduce class numbers. One reason was apparently research (from the United States) which showed that only a major reduction – say, from 25 to 15 – would significantly affect standards. And this, it was argued behind the scenes, would be too expensive. Classes in state primary schools now average 26, compared with 10.7 in the independent sector.

It seems self evident that many parents go private because each child is likely to receive more attention. The United Kingdom has some of the largest primary classes in the western world. More worrying, though, is that ministers' language on class sizes has changed. They no longer talk of pupil/teacher ratios, but of adult/teacher ratios – counting teachers and classroom assistants in the same way.

There can be no doubt that the army of classroom assistants recruited by Labour has been of great help to teachers – relieving them of tasks that they should not have been saddled with. The teachers' unions, however, argued from the start that they would be used as "cheap labour" to replace more expensive teachers. Eleven years on, their worst suspicions may be on the way to being confirmed.