Only 1 per cent of teachers think parents understand the new accountability measure Progress 8, according to a TES poll.
Tomorrow, schools will find out their Progress 8 score, which replaces the previous measure of five A* to C GCSE grades - including English and maths.
All schools will be ranked on the government's new performance measure for the first time this year.
But according to TES’ snap survey of nearly 1,000 respondents, nine in 10 teachers believe parents in their area still do not understand the measure.
And, of those respondents, 9 per cent of teachers said they thought parents were unclear on how Progress 8 works.
Duncan Baldwin, deputy director of policy at the Association of School and College Leaders, said: "Parents are going to struggle to know what this means [when the performance tables come out]."
He added: "I think it’s potentially very confusing."
The Department for Education uploaded a short video explaining Progress 8 and how to interpret scores last year.
But the poll reveals that only 1 in 100 teachers think parents will know what a score equates to tomorrow - when the key stage 4 performance tables are released.
Analysis of the provisional key stage 4 data released in October suggests that nearly 400 secondary schools could be classed as "coasting" under Progress 8.
Under the new coasting threshold – a Progress 8 score of less than -0.25 – an estimated 374 secondaries would be defined as coasting, the Education Policy Institute (EPI) revealed.
And further analysis from Education Datalab suggested that almost 300 schools could fall below the new floor standard - a Progress 8 score of -0.5.
These schools may come under increased scrutiny from Ofsted.
Click here for our poster on how Progress 8 works.
POLL: Teachers, do you believe the parents in your area understand the #Progress8 accountability measure?— TES (@tes) January 16, 2017