Education officials in Gunma Prefecture, north of Tokyo, say dozens of junior high school students suffered minor injuries when they were hit by hailstones as they were making their way home on Thursday.

The 87 junior high school students who were hurt, 6 of who were treated at hospital for bruising, were caught in a hailstorm on their way home after taking part in after-school activities.

The municipal board of education in Fujioka City on Friday issued an instruction to the 16 public schools under its jurisdiction to pay closer attention to thunder and other weather phenomena. School authorities were told to try to ensure that children can take cover indoors or get home early if inclement weather is on the way.

The board says it's regrettable that the students were injured.

It also notes that the schools monitored radar data and let students go home earlier than usual, but stressed the difficulty of making the right call given the unpredictability of the weather.

The board adds that it will teach schoolchildren how to ensure their own safety in rough weather.