Less than a third of parents with pupils at secondary school have heard of Progress 8, a survey published by the Department for Education shows.
Progress 8 replaced 5 A*-C (including English and mathematics) as the new headline measure of secondary school performance from 2016.
But only 30 per cent of out of a representative sample of 1,735 parents polled last summer said they had heard of it.
Awareness of the measure has grown, from 14 per cent in summer 2016 and 19 per cent in winter 2016.
However, the latest findings show that parents' understanding of how secondary schools are being judged and held accountable remains stubbornly low.
Among 1,635 secondary school pupils surveyed, 12 per cent had heard of Progress 8, whilst 77 per cent had not and the remaining 11 per cent replied "don't know", or did not answer.
Pupils 'don't know what EBacc is'
Many pupils also seemed unacquainted with the English Baccalaureate, in which pupils study English, maths, science, history or geography, and a language.
The government wants 75 per cent of Year 10 pupils in state-funded mainstream schools who are taking their exams to study for the EBacc by 2022.
Just half (51 per cent) of pupils in Year 9 and above said they had heard of the EBacc – an increase on last winter's 40 per cent.
A higher proportion – 60 per cent – of parents had heard of it, similar to previous surveys.