Some 70% of children from Japanese households with an annual income of less than ¥3 million ($20,540) take part in no after-school private lessons, according to a survey by a nonprofit organization.

Gaps are also seen in ways children spend after-school hours at home between low-income and other households.

"Disparities in after-school experiences may give broad impacts on children's learning and upbringing," said an official at Houkago NPO Afterschool, the organization.