Nine-year-old Lennox poured a large blob of red paint on to his palette. Reaching over for the glitter paints, he matched it with a dollop of sparkly red. “This is blood,” he announced, mingling the two together to form a glutinous liquid.

Then he dipped his finger in the mixture and slowly, carefully, wrote two words in large letters: HELP ME. Finally, he smeared paint over both hands and slapped them down on to the middle of the page.

“He wanted the image to look like someone who was severely injured, who needed help,” says Stephen Adams-Langley of school-based counselling charity The Place2Be. “But the powerless and injured victim was him.”

Schools are filled with pupils like Lennox: children who quietly juggle extraordinarily difficult home lives with the casual mundanities of school. One in 10 children between the ages of five and 16 suffers from a diagnosable mental-health disorder - equivalent to three pupils in every classroom. Of these, nearly 80,000 experience severe depression, including 8,700 children under the age of 10.

Indeed, the majority of adults with mental-health problems first experienced them in childhood, according to the mental-health charity YoungMinds.

Lennox may be unusual, therefore, but he is not unique. A number of teachers have been surprised, and then perturbed, to discover that disturbing images in artwork or essays are not the product of fevered schoolchild imaginations, but the outward expression of a complex, internal balancing act. Or, in some cases, an all-too-literal account of their lives.

“If a child is asked to write about something scary or something that’s made a big impression, they will take that literally,” says Phillip Hodson, fellow of the British Association for Counselling and Psychotherapy. “And some have troubled lives.”

Read the full story in this week’s TES magazine

Children’s names have been changed.

www.theplace2be.org.uk.