Schools should help teachers who come under pressure from students and parents to boost their grades, the exams regulator has said.
Ofqual says exam boards may intervene where "inappropriate pressure" has been placed on teachers judging grades.
It says such cases could be treated as potential malpractice.
Concerns have been raised that parents could try to influence grades given out by teacher assessment, after GCSE and A-level exams were cancelled this year.
A system based on teacher assessment was instead set up based on evidence, including coursework, essays and optional assessments by exam boards.
Head teachers have raised fears that the cancellation of exams and the move to teacher assessment would lead to pressure from parents with "pointy elbows and lawyer friends".
In its guidance on submitting grades, Ofqual says heads "should be careful to avoid teachers being put under pressure from students, parents or carers to submit grades that are higher than the evidence supports".
It suggests they "should keep records of such cases and might be required to report to the exam boards any cases where they believe inappropriate pressure is being put on teachers".
Last week, Ian Bauckham, interim chair of Ofqual, told a conference of head teachers that it would be "wrong and fundamentally unfair" if judgments were subject to pressure or interference by people "with a vested interest".
He warned that students could end up in destinations "for which they were ill-prepared" if this happened.
The exams regulator is urging teachers to question whether any of their judgments might be affected by factors not based on evidence of performance "such as unconscious beliefs or types of bias".
Judgments should not be affected by a student's behaviour, "character or personality, appearance, performance of their siblings, parental opinions or the knowledge of grades needed to meet a university offer", the guidance adds.
The document also provides information for schools about how to generate grades and the evidence that should be considered.
Exam boards will provide a package of support materials to help teachers make these judgements and will provide further advice on how centres should collect and submit evidence.
It says "the grades submitted to exam boards must reflect a fair, reasonable and carefully considered judgement of the student's performance across a range of evidence, on the curriculum content that they have been taught."