Pupils at a school in Japan’s southern Okinawa have sought shelter from US military aircraft nearly 700 times since an incident a year ago when a helicopter window fell into its schoolyard.

Osamu Tobaru, the principal at Futenma No. 2 Elementary School, told local media that he was reduced to tears by children having to evacuate from the outdoor playground numerous time during gym classes due to safety concerns caused by overhead aircraft.

Describing the fact that US aircraft is permitted to fly above the school – which is located next to a US military base - as a violation of children’s right to an education, Mr Tobaru told Jiji news agency: “I cried when I saw the children evacuating.”

It was on December 13 last year that the school discovered that a window from a CH-53E large transport helicopter, deployed to US Marine Corps Air Station Futenma in Ginowan, had fallen into its schoolyard.

Since then, school officials have installed shelters, surveillance cameras and security guards in order to ease security concerns over passing aircraft among parents and teachers alike, according to reports.