How can a policy which sounds like such a good idea in theory turn out to work so dreadfully in practice? This question defines one of the central paradoxes that drove me to write a book on arguably New Labour’s key education concept. This is exam-based accountability: the notion that by testing pupils regularly, publishing the results and then holding schools to account for the outcomes, standards will rise and the billions flowing towards education will benefit the country.

When I started covering the testing regime for the Times Educational Supplement, the idea that this structure would be effective in transforming our classrooms seemed persuasive. Now, after four years charting its side-effects, I am convinced that it is doing huge harm in our schools.

I am not the only one: last week England’s General Teaching Council became the latest in a long line of organisations to question the testing drive in its current incarnation. The need to maximise exam results now defines how teachers and schools behave to an extent not seen since Victorian times, when schools were funded according to how well their pupils fared in simple three Rs tests.

School league tables, targets, Ofsted inspections and teachers’ performance pay now all hinge on test results, reminding teachers, under a system I characterise as ‘hyper-accountability’, that raising exam scores is their raison d’etre. Yet it is far from clear that this is improving our schools in any sense other than helping teachers and politicians raise the narrow statistical indicators by which they are judged.

My book charts the downsides of hyper-accountability, for pupils. In their final year at primary school, a typical child can forget about a broad education as they are put through months of test preparation. Data from the government’s testing regulator show that, on average, schools devote nearly half the week to test practice for four months in the run-up to the key stage 2 tests in English, maths and science, or Sats. In the meantime, subjects such as PE, art and music are marginalised.

There are concerns that English pupils, who face more major tests than any others, are increasingly stressed as a result. I am not convinced that this is uniformly the case: pupils react differently to test pressure. But some primary children are certainly being put under strain over results because of their schools’ need to maximise the scores, even though the outcomes are of minimal importance to the pupil.

Other downsides include teachers feeling under so much pressure to improve GCSE grades, many tell their students what to write for coursework; schools pushing pupils en masse into vocational courses which have high league table value but are of questionable worth in the outside world; and schools focusing their attention on small groups of students believed to be working just below the level monitored by the government’s statistical indicators.

Because schools, under results pressure, are increasingly spoon feeding pupils towards success, children are sent the message that the teacher will do the thinking for them. And employers and universities are now routinely complaining that school leavers are not demonstrating the skills that the accountability system marginalises, such as lateral thinking and oral ability.

It is not even clear that improving national GCSE and A-level results are helpful, in their own right, for pupils, since if the national figures go up, employers and universities will simply demand higher grades from each school leaver.

The question, then, is not whether schools need to be held accountable, but whether the current system is serving pupils and the nation well. If, as I believe is undeniable, the answer is a resounding ‘no’, a radical rethink is needed.

I, and others, would replace the national system of Sats tests at 11 and 14 for all with testing only a small proportion of pupils, with the results used to hold ministers to account.

Parents would still have objective information on school quality, but through an enhanced system of Ofsted inspections, focusing on rounded judgments of school quality, rather than test scores.

Perhaps the book’s most damning finding is its evidence on how ministers have been urged to look into the downsides of test-based accountability, and repeatedly refused. They are trialling more regular testing for pupils, but this risks making schools even more test-driven. The suspicion is that narrow political considerations – changing the accountability system more fundamentally might be perceived as caving in to teachers’ unions, who have never supported it – explain the government’s intransigence.

But pupils, just as much as teachers, are the losers under this regime. If politicians refuse to even investigate serious change, effectively putting their own interests above children’s, they deserve to be punished at the ballot box.