There are warnings of confusion over university admissions from changes to GCSE exams in England which will create two different pass grades.
A number of universities have minimum entry grades at GCSE level – such as a C grade pass at maths and English.
But GCSEs are switching to numerical grades, from 9 to 1, and there is uncertainty because both 4 and 5 are officially classed as pass grades.
Universities are now setting different "pass" grade equivalents.
University College London says a C grade pass now requires a grade 5, while Manchester University has set the benchmark at grade 4.
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Deborah Streatfield, founder of careers advice charity My Big Career, said students and parents were "confused" and looking for advice.
"It's inconceivable that a simple task of deciding a pass has led to a ridiculous "standard pass" and a "good pass".
"Universities and employers need to decide whether a 4 or 5 is the benchmark.
"At the moment different standards across universities will lead to a divisive landscape leading to disadvantaged students losing out again."
Different types of 'pass'
Pupils taking their English and maths GCSEs this year will be the first to get the new numerical grades this summer – and these results will have an impact on university applications as well as getting on to A-level courses.
For pupils who get a grade 4 in English and maths, it means that they will already be below the threshold for some universities – even though it is a pass grade – and before they even begin their A-level courses.
The new numerical system will be phased in for other GCSE subjects over the next few years.
When the Education Secretary Justine Greening explained the new points system to the education select committee in March she said that grade 4 would be a "standard pass" and grade 5 would be a "strong pass".
She wrote to the committee chairman to clarify that grade 4 was the "equivalent to a C and above" – and that employers and universities would be expected to recognise the grade 4.
But there are different interpretations from different universities.
University College London says it expects applicants for all subjects to have a C grade at maths and English GCSE – but under the new system that will be a grade 5.
King's College London also makes a grade 5 an equivalent of a grade C for its admissions.
But Leeds, Manchester and Liverpool put grade 4 as their requirement.
London School of Economics, which previously required grade Bs, now requires a 5, although a B grade could also be the equivalent of a 6.
Oxford and Cambridge, which run their own tests and interview systems, do not have such across-the-board minimum requirements for GCSEs.
A spokesman for the exam regulator Ofqual said that it remained up to universities to set their admissions rules.
But the spokesman said that this year's GCSE candidates would not apply this year – and the requirements might be re-set again after the first wave of results.
Suzanne O'Farrell of the ASCL head teachers' union said that some schools might be "future proofing" their pupils' results by treating grade 5 as a pass rather than a grade 4.
But she said it would not be until next year that it would become apparent how universities would interpret the pass grade.
A Department for Education spokesman said that the changes were "part of our drive to continue raising standards" and a wide range of resources had been produced to explain the new grading system.
"Most recently every school and college have been sent a pack with information for teachers, students, parents, and employers."
A website had also been launched to answer questions people may have, he said.