Professor Alan Smithers, director of the centre for education and employment research at the University of Buckingham, said the Government must show strong leadership and make an immediate announcement about how schoolchildren will be assessed this summer.
A consultation about what will replace GCSEs and A-levels is under way. It includes proposals for teachers to decide on grades using evidence from mini tests as well as coursework and homework. But Mr Smithers said the consultation is delaying the process, and teenagers and teachers need clarity now.
He said: “I would like an announcement within days. There is no perfect solution so it’s much better to have something now which is agreed, and which gives shape and substance to the studies of pupils, than to have something perfect later in the year.
“It is understandable that some pupils are feeling lost and unmotivated. If you don’t know what the exact goals are how do you know what to concentrate on?”
The joint consultation between the Department for Education and Ofqual runs until January 29.
Students due to take exams have been asked to take part, as well as their parents, carers, teachers, school and college leaders, employers and heads.
Professor Smithers said: “I am not sure the consultation is helpful. They will get a wide variety of views and take a long time digesting those views.”
Last year GCSE and A-level results were mired in chaos after a discredited algorithm was used to work out grades. After a government U-turn, grades were recalculated based on teacher assessments only.
This year it is proposed that grades are based on teacher assessments, using evidence which could include short tests set by exam boards and marked by teachers.
Other evidence that could be used for teachers to base their grades on includes coursework, essays, tests and homework. Results could be given out in early July instead of late August.
Dr Tina Isaacs, honorary associate professor in educational assessment at UCL’s Institute of Education, told the Evening Standard there is no perfectly fair way of replacing A-Level and GCSE exams this year.
She said the best that students can hope for is a “fair enough” system. The current proposal is the “fairest” system possible in the circumstances, but some students will still miss out, she said.
Dr Isaacs said: “Given the situation we find ourselves in there is no system that can be absolutely fair to every individual because learning loss has been so uneven across the population.
“It’s not just regional, it’s school to school, college to college and child to child. Who has been isolating, and whose bubble has been sent home three times?”