Secondary school league tables are published at 09:30, featuring the results of the first pupils to sit new, tougher GCSEs in English and maths.
Parents and pupils in England will be able to compare how local schools are performing against each other.
The tables use raw GCSE results from last year and a raft of data from the Department for Education to evaluate how well pupils progress in a school.
Both Progress 8 and Attainment 8 take into account results of a pupil’s best eight GCSE results including English and maths.
Progress 8 also takes into account the educational level at which pupils entered the school.
Last summer, teenagers sat new, tougher GCSEs in English and maths, which were graded 9 to 1 (9 being the top grade). All other GCSEs are graded under the old-style alphabetical system.
Pupils are considered to have passed the new exams if they achieved a grade 4 or above – equivalent to the old C.
But for the purposes of school accountability (the school league tables), the Department for Education deems a grade 5 to be a pass.
This has led to some confusion and disquiet, with schools and individual pupils effectively being judged by different standards.
The data, published at 09:30 on Thursday, will show how many schools have missed the government’s floor standard of -0.5 in Progress 8.
‘Baffling for parents’
Geoff Barton, general secretary of the Association of School and College Leaders, said the secondary school performance tables could not be compared with previous years because the government had “once again moved the goalposts”.
“The new 9-1 grading system for GCSE English and maths has complicated the way in which the headline measures of school performance are calculated, with Attainment 8 and Progress 8 having to be worked out using a combination of 9-1 grades and the old A*-G grades,” he said.
“It is particularly frustrating that the bar for achievement in English and maths has been raised arbitrarily to a grade 5 under the new system, which is higher than the old standard of grade C.
“And it is potentially baffling for parents and employers that schools are now judged on grade 5 – described as a ‘strong pass’ – while grade 4 is good enough to be deemed a ‘standard pass’.”
Mr Barton said the tables revealed only a limited amount about the true quality of a school in a system undergoing significant change.