With the beginning of the new semester, schools in Japan are heading into uncharted waters as they battle a delta-driven explosion in COVID-19 cases, prompting some parents to decide not to send their children back to the classroom.

In some municipalities, elementary, middle and high schools resumed classes last week after a monthlong summer vacation. But for many students, Wednesday marked the first day back at school.

The school restart has coincided with a recent surge in the number of teens and preteens infected with the coronavirus, igniting controversy over whether it’s safe to allow pupils back into schools.