Japan's education ministry presented Friday the option of schools reopening for some grades only to reduce the risk of coronavirus infections, with priority given to classes for first- and sixth-graders at elementary schools as well as senior students at junior high schools.

The proposal was made to local education boards. Most schools across Japan have been closed since early March amid the spread of the virus.

Elementary school first- and sixth-graders as well as senior students at junior high will be prioritized because they have either just entered school in April, are in their final year or have to prepare for entrance exams next year.

The suggestion follows a meeting between the education ministry and a government panel of experts on Monday.

The ministry also proposed holding classes in smaller groups using several classrooms, providing boxed school lunches rather than having students serve food to each other and avoiding group sports.

While the nationwide state of emergency over the virus epidemic, originally scheduled to end next Wednesday, is expected to be extended for another month, education minister Koichi Hagiuda said not all schools need to remain closed as the situation varies from region to region.

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"If all schools follow the measures of the hardest-hit municipalities, classes will increasingly fall behind schedule," Hagiuda said, urging local authorities to reopen schools if possible based on their own judgement.

Noting some municipalities have already decided to extend school closures to the end of May, Hagiuda said it will be "a stretch" for them to make up for lost time and complete the academic year that will end next March.

In a related development, the prime minister's office has instructed relevant ministries to thrash out issues concerning the option of changing the start of the academic year to September, government sources said Friday.

The government hopes to sort out key issues as early as June before starting to discuss whether to introduce the new system from next year.

The move comes amid concerns that prolonged school closures due to the epidemic will result in students falling behind, or starting school at different times.

By matching the academic year to what is common in other parts of the world including Europe, the United States and China, the government also hopes to attract more foreign students, while making it easier for Japanese students to study abroad.

The University of Tokyo had begun to consider implementing a September academic year nine years ago, but subsequently abandoned the idea.

Hagiuda said Japan has so far seen no child deaths from COVID-19 and child-to-child infections at schools have not been reported. But he added that if a cluster of students infected with the virus is found, it will prevent schools nationwide from resuming.

As of April 22, about 95 percent of schools in Japan were closed, according to a survey by the ministry.