Pressure on private school pupils to get top grades is leading some to self-harm, a clinical psychologist has claimed.

Tanya Byron, a clinical psychologist and broadcaster, told headteachers at the Boarding Schools’ Association conference in York this afternoon that “it’s not an exaggeration to say there’s a mental health crisis in children and young people”.

She said colleagues in London were seeing “amazing young people” who are “coming in chopping into their arms because don’t get enough A*s, but their mate does, and they are not thin enough and they are not hench enough and they haven’t got the right six pack. It’s all about perfection.”

She added: “And I would say in the independent sector you see more of that than anything else because often these kids come from families that are very aspirational.

“With respect to you all, because I understand you are businesses, you have to protect your brand and you have to get the grades, but at what cost? That’s all I’m asking you.

“What are we doing for children young people? Are they rounded? Are they resilient? I would argue no.”

Warnings over 13 Reasons Why

When challenged by one head, she said said she “totally agreed” there was similar pressure in the state sector caused by league tables and the need to protect brands.

However, she added that the biggest group of problems that are growing are “amongst children of families that you see”, and added: “I would argue the mental health difficulties within the independent school sector is huge”.

Julie Robinson, general secretary of the Independent Schools Council, said: “I think our schools are particularly good on pastoral care and support. There is very good tutoring. Particularly in boarding, you’ve got house parents, you’ve got tutors, you’ve got layers and layers of pastoral care. And that’s one of the benefits - the wrap around care for the whole child.”

Professor Byron also urged heads to write to parents and talk to children about the popular Netflix series 13 Reasons Why, which she said “really glamorises suicide”.

She said: “There’s no problem with talking about these things, but when you see these things put out there as drama in a way that’s glamorising things, and also particularly children and young people are watching these things but we as adults are not aware of it, and we are not talking about it and we are not debating about it with them and getting them to critically evaluate what they are looking at, we are not asking them questions, that’s when it becomes a problem.”