School league tables and performance measures are skewing and narrowing the curriculum, according to the findings of a heavyweight education commission.

The NAHT heads’ union’s School Accountability Commission will warn that government tables and targets are distorting schools’ behaviour and do not work in the interests of pupils, parents or the government. 

It highlights how primary schools drilling for Sats has become common, with some schools even running revision classes and practice tests during school holidays.

The commission, which includes a range of experts from across the sector, also warns that comparing the performance of pupils at schools in different settings has been proved to be unreliable but is still being used to judge how effective schools are.

The NAHT launched the commission earlier this year to assess the impact that the current high-stakes accountability system was having on English schools.

The Improving School Accountability report, being published later this week, highlights how performance measures and tests are distorting schools’ behaviour rather than helping them to improve.

The commission’s findings follows a Tes survey earlier this year which found that one in five schools has been sending its six- and seven-year-old pupils home with practice Sats papers.

‘A shadow of fear’ over schools

Two-thirds of teachers also said their schools were holding mock Sats for children at key stage 1.

And last month Tes revealed how 11-year-olds were being prepared for their GCSEs five years in advance by being made to sit specially-designed tests modelled on the exams, 

The NAHT-led Commission blames the pressure of the accountability system for schools’ decision-making.

It says schools are encouraged to focus on areas that are critical as performance indicators.

The commission highlights the EBacc - which was created to encouraged schools to pursue traditional academic subjects at GCSE - and Progress 8 as other measures which have changed the way in which schools behave.

The report recognises the importance of having a core of academic of subjects but warns that an over-emphasis on them “has skewed and narrowed the curriculum.”

The new report also warns that “the use of narrow data impedes a broader evaluation of effectiveness of a school’s curriculum in meeting the needs of the pupil cohort that it serves and the extent to which this prepares pupils for the future.”

Nick Brook, the deputy general secretary of the NAHT, who chaired the commission, said: “Performance tables and Ofsted were introduced over a quarter of a century ago to hold schools to account but are no longer working in the interests of all pupils and parents, schools or government.

“Comparison of pupil performance data between different schools in different contexts has proven to be unreliable, yet this continues to drive judgements of school effectiveness.”

Earlier this year, the new education secretary, Damian Hinds, signalled a major change of direction on school accountability when he announced that the government was planning to replace minimum floor targets and the coasting school measure with one way of holding schools to account  - which it is planning to consult on.

The Commission report welcomes this and warns that using targets based on exam results as a trigger for intervening in schools is too crude.

The report adds: “Coasting and floor standards have cast a long shadow of fear over many schools and school leaders.”

Last year, the NAHT 2017 Assessment Review Group report, Redressing the Balance, called for the use of floor standards and coasting standards to determine intervention in individual schools to be stopped.

The new report says: “Data should only ever be the starting point in a conversation about school standards and effectiveness. Statutory tests and exams will never be able to capture all aspects of a young person’s progress or a school’ success. “

“Nevertheless, academic success is vitally important to the future life chances and the progress that young people make towards achieving it will always be a key indicator of school effectiveness.”

The Commission report, which will be published on Friday, delivers a damning verdict on the school accountability system.

It warns that measuring school performance through Ofsted and league tables is failing by holding back improvement, driving teachers out of the profession and discouraging teachers from working in challenging schools where they are needed most.