Enrolment in such mail-order courses is rising by about 25 per cent each year. The Benesse Corporation, a pioneer of the idea, has seen demand grow from 70,000 students in 1987 to 1.25 million this year.
Parents are hoping the course materials and correcting sheets which arrive at their homes every month will give their children a head start in the fierce competition for university places.
When the latest mail-order education package for three-year-old Keiko Sato of Yokohama city arrives she cannot wait to get at the new video and audio cassettes, says her mother, Rie.
"She adores the cartoon characters they use on the course materials and gets a great kick out of putting some of the cut-out projects together. We enrolled her in the course before her third birthday when I took the decision with my husband not to send her to pre-school just yet. The course seemed to offer a great opportunity to introduce her to things she might learn at pre-school without her having to leave the security of the home."
Several companies cater for parents like Mr and Mrs Sato. Benesse offers five courses for children up to the age of six under the title Kodomo (Children's) Challenge.
Its pre-school course for two to three-year-olds emphasises learning through play. According to the company, the course uses audio-visual materials and educational books to stimulate the children while encouraging individuality.
The Petit course for one to two- year-olds relies on picture books, and videos to "instil curiosity".
The courses are cheap, which is another reason for their success. A typical Children's Challenge monthly package, which also includes a parents' magazine, costs 1,600 yen (Pounds 7.44) a month - not much more than the price of a glossy woman's' magazine in Japan.
In Taiwan, the Children's Challenge is offered under the name Shaoponyu Challenge. Launched eight years ago, the programme now has 50,000 pre-schoolers on roll and its main cartoon character, Shimajiro, is a familiar sight to many Taiwanese children.