Schools are struggling to cope with an influx of pupils who can't speak, read or write Japanese.
The pupils are the children of immigrant workers, huge numbers of whom have been attracted to Japan by recent changes in immigration laws.
The increase is particularly high in schools in industrial centres, such as Hamamatsu to the west of Tokyo, home of Yamaha, the motorbike and musical instrument manufacturers.
Around 16,000 foreign nationals are now living in Hamamatsu and 1,000 non-Japanese pupils have enrolled in the city's schools. Most are Brazilians of Japanese descent.
Nationwide, the number of foreign students attending elementary and high schools has reached 100,000. The largest group are of North Korean origin. But many schools which have attracted immigrant pupils say they don't have the staff and resources to help them.
Language teacher Yuki Nishimura says: "Japanese schools are used to dealing with large homogeneous classes in which every pupil is expected to move forward at the same pace. There are few facilities for pupils who have individual needs."
Schools are also unsure about the best way to help immigrant pupils.
Some teachers and administrators say that foreign pupils should be integrated into mainstream classes where they will be able to pick up the Japanese language and complete their high-school diplomas.
Other teachers say that most foreign pupils require individual help with their reading, writing and speaking skills and should be taught in separate classes with specialist language teachers.
Most teachers agree that Japan requires a national strategy, and pool of resources, for helping schools cope. Those teaching non-Japanese-speaking pupils say they also require strategies for communicating with parents who speak very little Japanese and cannot read the letters and information leaflets that are an important element of school-home links.
A survey carried out by Tokyo University of Foreign Studies revealed that more than 80 per cent of immigrant parents are unable to read Japan's complicated written language. But the enrolment of immigrant pupils is also encouraging schools to reassess the sort of education they are providing.
Yuki Nishimura says: "The presence of young people with different cultural backgrounds is helping to break down the idea that Japan is a homogeneous nation in which no one is allowed to stand out.
"Teachers are learning to accept the idea that all young people have individual needs which have to be dealt with."