Daniel Downes is a secondary school teacher in Buckinghamshire.

The Department for Education League tables, released this week, show that a staggering 1,500 schools are falling behind the national average.

According to the Telegraph, this has meant that almost a quarter of a million students are at schools with a negative Progress 8 rating. This is against a backdrop of increasingly high OFSTED ratings and a steady incline in GCSE results for pupils, so what is actually happening?

First of all, if you set an ‘average’ for schools, a large number of them will be below that average. Approximately, you might expect, the same amount as those that are performing above average. This is because that is how averages work. An average is specifically calculated to give an approximation for a value in the ‘middle’ of a spread of data. If they didn’t, averages would be useless.

In that case – and not to get too ‘mathsy’ here – calculating standard deviation for schools (the distance between a school’s performance and the average) would be more useful than creating a media panic about below average schools.

What about this Progress 8? Well there’s a lot more maths there I’m afraid. Subjects are categorised into ‘buckets’ or ‘elements’, of which there are three.

The first contains the core subjects of Maths and English, which are double weighted in the calculations. Then comes the ‘Ebacc’ element of sciences, languages and humanities. Finally, there is the ‘open’ element, containing creative subjects and others that didn’t fit into either of the first two.

The idea is that students and schools are given a number. Achieving ‘0’ would mean that students made the expected levels of progress throughout their school career, a ‘+1’ indicating that they have made one grade above their expected level in each subject on average and a ‘-1’ would indicate the opposite.

The whole school score would then generate a general figure to indicate progress that students would make across subjects. So, the news that nearly 250,000 students attend schools where their Progress 8 figure is negative would suggest that in those schools students did not tend to make their expected progress.

But there are some problems with measuring progress in this way, issues that have a negative impact on the education of our young people and limit the ability of schools to innovate and direct their own curriculum.

The first should be clear; the embedded hierarchy of subjects, starting with the kings of Maths and English to the peasants of art, drama and music. As a Head of Maths at a Secondary school, this brings with it certain silver linings but also accompanying clouds.

What is not clear is why a student should be punished for having talents in one subject over another, or why a school with a subject specialism in computing or sport should not be able to celebrate those achievements but instead side-line them to ensure that their headline figures look good.

Of course it is important that students leave schools with high levels of literacy and numeracy, but what is not clear is why it is that they should necessarily have a better understanding of trigonometry than they do of how to read sheet music.

Part of education should be guiding students to embrace their talents, to play with them and explore them, and to find pleasure and value in them. Why would we measure a school by their ability to ignore the individual needs of a student in order to satisfy an arbitrarily defined formula?

Children will be forced to take GCSE options that they do not want to in order to ensure that the school can demonstrate a good performance. Some of those creative subjects will have to be removed from the curriculum in order to timetable the extra Maths and English lessons that schools will need to reflect their importance in the headline measure.

Students will therefore receive a narrower education when they need a broader one. Whilst this has already happened to an extent with the A*-C (including English and Maths) headline measure, it can only get much, much worse.

Further, it is well documented that students from disadvantaged backgrounds, lower abilities, and those with Special Educational Needs progress at lower and slower rates. This means that a school with high numbers of these students will be limited as to the ‘score’ that they can achieve against these measures.

This will particularly hit schools that are in selective areas but are not grammar schools, that tend to have large numbers of pupils from each of those three categories.

Naturally, it is important to set a high bar for all schools to aim for, and there is no reason why all schools shouldn’t aim for the highest levels of progress for all of their students, but measuring against a national average will always doom certain schools to be below that line.

This will mean that parents will not want to send their children there, their pupil numbers will deteriorate, and with it their funding. The diminishing funds of these schools will then send them into a spiral of worse results, lower pupil intakes, and so on. That hardly seems like a water-tight model for raising standards.

The national results demonstrate the impact of this flawed thinking. There is a huge geographical divide between the best schools, concentrated in London, with the highest progress rating and those in the North, where the majority of schools came out with negative ratings.

A great number of the highest performers were Grammar schools, which you would expect in a system that gives them a phenomenal advantage. Free schools and Foundation schools, the education establishments with the greatest autonomy to innovate and design curricula that are catered directly for their students, are the worst performing schools in the country.

The Progress 8 measure punishes localism by allowing communities to open their own schools but nationalising the parameters by which they must succeed.

We need a debate about how we measure the effectiveness of a school. Perhaps we should begin with why we assess the performance of schools in the first place; what are we looking for? What is a successful school?

Do we really want the only successful schools to be the ones that are the best at conforming to a narrow conception of academic performance, or do we want a little more for our children than simply that?