Headteachers are to publish their own alternative league tables which they say will give parents more information about schools than data published by the Government.

The rival rankings, which will focus on secondary schools to begin with, are expected to cover GCSE results as well as details on extra-curricular activities such as music and sport, the curriculum and other measures like class sizes and subjects.

School leaders said they believe that the new tables will become the established, independent way of publishing data that bypasses politicians and government.

The proposals have been drawn up by two unions - the Association of School and College Leaders (ASCL) and the National Association of Head Teachers (NAHT), along with independent school and academy group United Learning and PiXL, which works with schools to raise standards.

It comes amid concerns among school leaders about current school league tables, including a decision made by the Government last year that only a pupil's first attempt at an exam will count towards their school's overall results, a change made due to concerns that students were being entered for qualifications early, or multiple times to boost grades.

Jon Coles, chief executive of United Learning, said that over time, performance has become less about giving parents information and instead become a way for successive governments to attempt to influence the decisions that headteachers make about running their schools.

'This is too crude an approach to defining a great school or encouraging improvement and at different times, it has been detrimental in different ways,' he said.

'For example, promoting too much focus on the C/D borderline, especially in English and maths, or promoting choices of qualification which do not serve individual children well.

'What parents want to know and what heads want to offer is much greater than the predominant focus on any single measure would suggest. Exam data is of course a key element of this, but it's not the only one that parents are interested in and it's not the only one that defines how well a school is doing.'

Mr Coles, who previously worked as a senior civil servant at the Department for Education, said that they would be asking parents what extra information they want to know, such as whether children can learn a musical instrument, if there are sports teams at a school or if it runs a Duke of Edinburgh award scheme.

ASCL general secretary Brian Lightman said that his members believe that the Government's decision to only include the results of a student's first exam entry was a mistake.

'If people want to look at first entry results they can, ultimately the final results are the ones that really matter. That was the driving reason why we want to be part of this initiative..

'As an association, we have always believed in openness and fully recognise the importance of accountability,' Mr Lightman said.

'We want parents to have access to data they can use in a format they can use it.'

Under the plans, secondary schools in England are being asked to submit their GCSE results for this summer - due to be released next week - which will then be published on a new website later in the autumn, before the Department for Education publishes its data in January.

Once released, the official data will form part of the information available on the new website - schoolperformancetables.org.uk - meaning that the vast majority of secondary schools will have at least some results.

Parents will be able to use the site - to compare up to five local schools, the organisations said - and choose what measure they want to look at.

The data will be built up over the next three years, and could later be extended to cover A-levels and primary schools.