Think of how closely squeezed the sticky rice is in sushi rolls and you have an idea of how dense the classrooms can be in Japan. In the years after the war, the average class had around 60 pupils. It was then the phrase sushi zume - which roughly translates as "as jam-packed as the rice in sushi" - began to be used to describe classrooms.
Today, class sizes are smaller, but they remain of national concern as the upper limit of 40 pupils is far above the Organisation for Economic Co- operation and Development average.
Since the 1950s, parents and educators have repeatedly called for the over-crowding to be addressed. But Japan's long-ruling Liberal Democratic Party (LDP), which had an almost unbroken rule from 1955 to 2009, only budged twice, grudgingly: once in the 1960s to bring the maximum down to 45, then in the 1980s to 40.
The new Government of the Democratic Party of Japan is now beginning to make good on an election promise that it would hire more teachers to thin out classes.
The traditional excuse for refusing to do more was a lack of money in the education budget. This would be more persuasive if Japan was not one of the richest countries in the world - number two in terms of economic might. Yet it spends one of the smallest percentages of its GDP on state education - 3.5 per cent, compared with 5.7 per cent in France.
Demographics may now make a difference: shrinking families are causing the school population to dwindle. But the response from schools has been simply to cram all their pupils into one superclass the moment the intake has dropped below 41.
The new Government's policy is to promote the individual, in order for the Japanese to become more creative and better competitors in the global marketplace.
Perhaps those big classrooms of passive learners made Japan what it is today - hardworking, with a strong bent for group consensus. But, given that the boisterous and individually-minded behaviour of young people is now making traditional command-and-control teaching nigh on impossible, the young seem to have voted already on what they think of being treated like sushi rice.