Peter Clarke, the former director of ChildLine Wales, believes stressed teachers create stressed pupils. He said both ChildLine and the Samaritans report an increase in calls for help at examination time each year because of suicidal thoughts.
Anita Cook, head of Bedwas comprehensive, Caerphilly, said high-ability children suffered particularly: "They've done well so far but know the crunch is coming," she said.
Her school has a range of stategies to help deal with student problems, including learning-related stress, and has set up a help clinic called the "zone" where they can talk confidentially to outside professionals.
It was recognised earlier this year by the Welh Secondary Schools Association as one of 15 schools providing outstanding support to pupils.
She said: "We've been aware of this problem for a number of years and now have a strong team of pastoral tutors and managerial staff - supported by outside professionals - to help pupils cope with the stress of preparation for exams and the huge volume of course work.
Mr Clarke has spent a large part of the first seven weeks in his new job meeting pupils.
Although so far the evidence is only anecdotal, he is particularly concerned that the climate of testing - even if not all of it directly involves children - creates a stressful environment for them.
He said: "Primary children now have to sit 30 national tests, and GCSE students might have taken more than 40 exams while at school. The new A-level curriculum means even more exams."