The Liberal Democrat's assertion that they will scrap SATs for seven to 14 year olds should they win the next general election is an interesting development in the ever-raging debate around assessment. Hardly a week goes by without an academic, interest group or think tank expressing contradictory opinions over their effectiveness as a means of gauging a child's potential, encouraging learning or educating society more generally.

Two weeks ago The Guardian carried an interview with the Head of Psychology at the University of Hull, Dr Peter Clough, who believes tests help prepare kids for later life. Last week, however, Philip Pullman, Michael Rosen, Jacqueline Wilson and the National Association of Head Teachers added their names to a campaign against SATs. Throughout education, opinions range from the thunderously evangelical to the strictest of abolitionists.

At Teacher Support Network, we know one thing for certain about the formal assessment of pupils. Many teachers who use our advice services report that they put a massive strain on their emotional wellbeing. The intensity of preparations and the all-consuming focus on results can contribute to debilitating stress levels and damage education through injury to staff - whether it's through time off, reducing teachers' confidence or encouraging many to leave the profession altogether.

Despite the breadth of opinion on tests, many of our callers believe that they devalue teaching. Parents seem to agree that it is an ineffective measurement of their children's performance: DCSF statistics show that only eight per cent believe that school reports and tests accurately inform them of their offspring's performance, compared to 28 per cent who believe that informal conversations with teachers is the best method (and 19 who prefer parents' evenings).

One thing that I'm pretty sure of, however, is that the basic premise of almost all examinations is that pupils are tested by their ability to get things right. There is no exercise in the country, to my knowledge, where pupils are expected to congregate in the gymnasium, sit down in silence and use all their cognitive ability to get as much as possible wrong. And no school finds any value whatsoever in diagnosing an improvement in a pupils' performance as not representing progress and then labelling them a failure.

A pity, then, that the assessment of schools themselves is not based on such rudimentary principles.

Last week the Secretary of State for Children, Schools and Families, Ed Balls, produced a hit list of 638 schools deemed as failures that, without action within 50 days, could face closure. However, by the Government's own figures, 30 of these schools are in the top five per cent of schools in the country.

Balls' figure is taken by the arbitrary formulation that for seventy per cent of pupils to fail to obtain five good GCSEs (including maths and English) is to fail as an institution to such an extent that it is suitable for the Government to issue a final - and entirely public - warning. However, in other circumstances, the Government uses figures that take into consideration both how much the pupil has improved since his or her arrival and the child's background.

School communities that have been rightly feted recently for astonishing results in very difficult circumstances now face public condemnation from the most powerful man in education and must operate with the constant fear of an axe hanging over their heads. The effects on the confidence and enthusiasm of these communities - not least the often already overworked teachers - will be disastrous.

The Government's policy is a worrying development. Not only is the pressure put on school communities through such public derision counterproductive, it has also been applied using unseemly criteria. With about half of pupils across the country failing to achieve the standards that Balls' uses as his yardstick of success, it is impossible not to conclude that factors outside of individual schools lie behind their inability to measure up to the Government's judgment.

It seems bizarre that, rather than emphasising the progress that these schools have made whilst operating under Labour's time in government, the DCSF has chosen instead to condemn them. While there is nothing new about schools being used for patently political purposes, Balls' National Challenge scheme seems based on a shocking neglect of the efforts of teachers, parents and pupils at those institutions named.

For the sake of aiding their efforts and simple consistency, such schools should not be threatened with closure. Our experience of coaching hundreds of thousands of teachers has shown that praise and encouragement are far more effective agents of change.

Teacher Support Network Chief Executive Patrick Nash is a regular contributor to SecEd, the publication for secondary education workers. This is his first column. You can find it and much more at SecEd's website.