MADRID — Over 8 million schoolchildren and teenagers in Spain are returning to classes this week with masks and efforts to keep social distancing, while authorities try to boost the vaccination rates among students.

Coronavirus cases have dropped from just over 700 per 100,000 residents in 14 days at the end of July to 177 on Monday, a level not seen since the beginning of the summer. Deaths for COVID-19 patients have stubbornly remained well over 100 per day for weeks.

But the staggered return to schools, which varies depending on regions and age groups, has been a cause of concern because vaccinations among the youngest started only in the past few weeks.

About 40% of students over 12 have received the two vaccine doses required to build the optimum level of immunization. Although Spain has little vaccine hesitancy, the government has launched campaigns on social media to motivate teenagers to get their shots.

Officials are betting on in-class education for this year, with no remote classes. Pupils will need to wear masks in classrooms and during recess time.