School coursework submitted by pupils sitting National 5 subjects will not be marked due to the coronavirus pandemic, the Scottish Qualifications Authority (SQA) has said.
The move follows the announcement that coursework for Higher and Advanced Higher courses would not be marked.
Teachers are instead being asked to use their professional judgement to estimate students' grades.
Exams have been cancelled this year in the wake of the Covid-19 outbreak.
The SQA has now updated its advice to parents and teachers about how pupils' grades will be determined this year.
It says teachers and lecturers should "continue to exercise their professional judgement" and estimate a grade and band based on a student's "demonstrated and inferred attainment of the required skills, knowledge and understanding".
Teachers will be asked to place their pupils in one of a series of bands of achievement, and will then be asked to rank individuals within each estimated grade.
This process may be informed by previous subject and qualification performance, and any prior attainment information where that is available.
The SQA says schools and colleges do not need to set additional mock or prelim exams, or homework, to help estimate a student's grade.
Teachers and lecturers are also not required to mark other work that would have been externally marked by SQA.
The exams body has already received coursework for a range of National 5 subjects.
However, Fiona Robertson - the SQA's chief executive and Scotland's chief examiner - said: "It has become clear that we can no longer proceed with the marking of the National 5 coursework received to date, in a safe and secure manner, that maintains the integrity of national standards."
She acknowledged that this would disappoint many people, but said the work could still be used in the future as part of the appeals process.
'Exceptionally difficult time'
It has also been announced that the deadline for teachers to submit grade estimations has been extended until 29 May.
This covers National 5, Higher and Advanced Higher courses and will make up the "core" of the results.
Ms Robertson added: "I would like to thank everyone involved in Scottish education for their support and patience during this exceptionally difficult time.
"I fully appreciate that this is an uncertain time for learners who have worked hard throughout the year and will now, with their families, be worried about what this means for them.
"By working together, we can ensure that their hard work is rightly and fairly recognised through our qualifications system."