Three-quarters of parents and carers have not heard of the new accountability measure Progress 8, according to a new survey.
And of those who have heard of Progress 8, less than a fifth (19 per cent) of parents and carers understand how it works, a poll finds.
In January this year, all schools were ranked on the government's new performance measure in the key stage 4 performance tables.
Progress 8 – which was used for the first time this year – replaced the previous measure of five A* to C GCSE grades, including English and maths.
But a survey of more than 1,500 parents and carers of secondary school children has revealed that only 19 per cent have heard of Progress 8.
And there is still confusion about the GCSE grading reforms, which come into effect this summer for maths and English. A fifth of parents and carers have not heard of the new numerical 9 to 1 scale which will replace A* to G.
And of those who have heard, only 16 per cent totally understand the rationale for the reforms.
This follows a survey from the CBI this week which revealed that more than a third of business do not know that the new numerical grading system for GCSEs is being used from next month.
Today's poll, released by the Department for Education, also reveals that fewer parents have heard of the English Baccalaureate (EBacc) – one of the government's accountability measures – than last summer.
Only half of parents and carers had heard of the EBacc, compared to 58 per cent last year, despite a push from ministers to increase the number of pupils studying the core academic EBacc subjects.