NARAHA, Japan — The children returned to Naraha this spring.

For more than four years, residents were barred from this hamlet in Fukushima after an earthquake and tsunami caused a meltdown at a nuclear power plant north of town. When the government lifted the evacuation order in 2015, those who returned were mostly the elderly, who figured coming home was worth the residual radiation risk.

But this month, six years after the disaster, 105 students turned up at Naraha Elementary and Junior High School for the beginning of the Japanese school year.

Every morning, cafeteria workers measure the radiation in fresh ingredients used in lunches. In some grades, as few as six students take their lessons in classrooms built to accommodate as many as 30. There are not enough junior high students to field a baseball team on the new field next to the school.

Yet the return of the schoolchildren, the youngest of whom were born the year of the disaster, has been a powerful sign of renewal in this town, which is in the original 12-mile exclusion zone around the Fukushima plant.