Struggling pupils told counsellors that they experienced panic attacks, excessive crying and even suicidal thoughts.
This report comes in the week that 11-year-olds across England take their Sats tests and as teenagers start preparations for their upcoming GCSEs and A-levels.
The numbers of exam-related sessions has risen 11 per cent over the last two years, the NSPCC-run service said.
Children aged 12 to 15 are the most likely to seek help over exam stress, but this year the biggest rise was among 16-18-year-olds, many of whom will have been studying for A-levels.
Dame Esther Rantzen, Childline's founder and president said: "I am very distressed that so many young people are turning to Childline because they have nobody else to confide in safely when they are desperately anxious."
NSPCC chief executive Peter Wanless, said: "Exams are important but worrying and panicking about them can be counter-productive, leaving young people unable to revise and prepare.
"It is vital that young people are supported by family, friends and teachers during the exam period to help them do the best they can."
Rachel Newham, a youth worker trainer from the Christian mental health charity Think Twice, told Premier that there were practical things that the church should do to help students in their congregations including praying for them. She said, "The whole church can be praying when exams are going on".