It is "morally wrong" to undermine teenagers' GCSE efforts with talk that the exams are too easy, a school leader has said.
Pupils are working extremely hard, and should not be told that their achievements are not enough, according to Brian Lightman, general secretary of the Association of School and College Leaders (ASCL).
With less than a week to go before youngsters receive their GCSE results, now is the time to celebrate their success, he said.
"I think we've got to be very careful with the message we send out about quality, it's potentially very dangerous to undermine confidence in the system. The fact of the matter is children are working extremely hard and teachers are working extremely hard to get them through exams."
Children are doing "everything asked of them," Mr Lightman said.
"They are working really hard and taking exams that are rigorous. They shouldn't be told that their achievements are not good enough. I think they get terribly frustrated by this. It's just wrong, it's morally wrong to undermine their efforts."
Mr Lightman said there were concerns about "comments that we need to have more rigour in the system and that exams are too easy".
More young people are completing their exams at 16, with higher grades than we have ever had before, he said. "What we should be doing next week is celebrating achievements and the enormous effort that has gone in by pupils and teachers," he added.
The future of GCSEs has been under the microscope in recent months. It was reported in June that Education Secretary Michael Gove was considering proposals to ditch GCSEs in favour of a return to O-level-style qualifications, with less able pupils taking simpler CSE-type exams.
The leaked plans resulted in an outcry that it would lead to a two-tier system and thousands of teenagers being branded as failures. Mr Gove later said that he would like to see all students sit O-level-type exams at some point in their school career. He has argued that a two-tier system already exists and radical changes are needed to make exams tougher and ensure that the UK keeps up with other nations.