Labour leader Ed Miliband said the NHS and councils should ensure that children can access counselling to help them cope with the pressures they face growing up.
"Children face new pressures growing up in Britain today, from internet bullying to other stresses and strains that they carry with them from the home," Mr Miliband said.
The Labour leader said three children in every classroom have a mental health problem, but schemes providing counselling and support had been downgraded.
Acknowledging that politicians had not taken mental health seriously enough in the past, he said a Labour government would give NHS patients the same rights to psychological talking therapies as they currently have for drugs and medical treatment.
Writing in the Sunday Express, he said mental health was a "crucial issue" for schools.