Sturdy leather bag known as randoseru can weigh 4-10kg when full, leaving students in pain and wanting something lighter

It’s a familiar sight every weekday morning and afternoon all over Japan: children as young as six creaking under the strain of a leather backpack crammed with textbooks.

The randoseru – a Japanese derivation of ransel, the obsolete Dutch word for backpack – is a fixture of primary school education, a repository for everything a child needs to get through a day at school.