An NHK survey has found that more than four in 10 public senior high schools in Japan saw new enrollments fall below their capacities this past spring.
Japan's declining birthrate is believed to be behind the shortage of applicants.
NHK surveyed education boards nationwide over entrance exams held early this year.
The broadcaster learned that as of April, the start of the current academic year, the number of entrants was below the places available at 1,437 schools.
That accounts for more than 43 percent of all full-time public schools in Japan, including branch schools. The figure does not include part-time, evening schools.
By prefecture, Kochi had the highest ratio of below-capacity enrollments, at 91 percent, followed by 88 percent in Shimane and Kagoshima, while Tokyo had the lowest at 10 percent.
As Japan's birthrate drops, the education ministry figures show that the number of graduates from public and private junior high schools has fallen by almost half over the past 30 years to 1.11 million people.
Taisho University Professor of Education Taro Urasaki says declining enrollment numbers may lead to a loss of quality in education because the number of teachers may be reduced and extra-curricular activities curbed.
Urasaki suggests that schools seek the cooperation of local communities to strengthen their distinctive features. He says this will also help their graduates to take root in the communities.