26 April 2021, North Rhine-Westphalia, Warendorf: High-backed chairs stand in an empty classroom at the comprehensive school in the town of Warendorf. In many places it is the first working day with the new Corona emergency brake, daycare centres and schools remain closed in many districts and cities. Photo: Guido Kirchner/dpa

26 April 2021, North Rhine-Westphalia, Warendorf: High-backed chairs stand in an empty classroom at the comprehensive school in the town of Warendorf. In many places it is the first working day with the new Corona emergency brake, daycare centres and schools remain closed in many districts and cities. Photo: Guido Kirchner/dpa

26 April 2021, North Rhine-Westphalia, Warendorf: High-backed chairs stand in an empty classroom at the comprehensive school in the town of Warendorf. In many places it is the first working day with the new Corona emergency brake, daycare centres and schools remain closed in many districts and cities. Photo: Guido Kirchner/dpa

26 April 2021, North Rhine-Westphalia, Warendorf: High-backed chairs stand in an empty classroom at the comprehensive school in the town of Warendorf. In many places it is the first working day with the new Corona emergency brake, daycare centres and schools remain closed in many districts and cities. Photo: Guido Kirchner/dpa

26 April 2021, North Rhine-Westphalia, Warendorf: Four students of a graduating class walk across the empty schoolyard at the comprehensive school of the city of Warendorf and cast their shadow on the ground. Recorded with a drone. In many places it is the first working day with the new Corona emergency brake, daycare centers and schools remain closed in many districts and cities. Photo: Guido Kirchner/dpa

26 April 2021, North Rhine-Westphalia, Warendorf: Trees cast their shadow on the empty schoolyard at the comprehensive school of the city of Warendorf. Taken with a drone. In many places it is the first working day with the new Corona emergency brake, daycare centres and schools remain closed in many districts and cities. Photo: Guido Kirchner/dpa

26 April 2021, North Rhine-Westphalia, Warendorf: Two empty schoolyards are seen on Monday morning at the comprehensive school of the city of Warendorf. Recorded with a drone. In many places it is the first working day with the new Corona emergency brake, daycare centers and schools remain closed in many districts and cities. Photo: Guido Kirchner/dpa

26 April 2021, North Rhine-Westphalia, Warendorf: High-backed chairs stand in an empty classroom at the comprehensive school in the town of Warendorf. In many places it is the first working day with the new Corona emergency brake, daycare centres and schools remain closed in many districts and cities. Photo: Guido Kirchner/dpa

26 April 2021, North Rhine-Westphalia, Warendorf: Four students of a graduating class walk across the empty schoolyard at the comprehensive school of the city of Warendorf and cast their shadow on the ground. Recorded with a drone. In many places it is the first working day with the new Corona emergency brake, daycare centers and schools remain closed in many districts and cities. Photo: Guido Kirchner/dpa

26 April 2021, North Rhine-Westphalia, Warendorf: Four students of a graduating class walk across the empty schoolyard at the comprehensive school of the city of Warendorf and cast their shadow on the ground. Recorded with a drone. In many places it is the first working day with the new Corona emergency brake, daycare centers and schools remain closed in many districts and cities. Photo: Guido Kirchner/dpa

21 April 2021, Mecklenburg-Western Pomerania, Lubz: The chairs in a subject cabinet of the Eldenburg-Gymnasium are raised. The state government in Mecklenburg-Vorpommern is sticking to the statewide closures of schools, daycare centers and many businesses. Only from a statewide 7-day incidence value below 100, the Corona protection measures are to be relaxed again. Photo: Jens Buttner/dpa-Zentralbild/ZB

21 April 2021, Mecklenburg-Western Pomerania, Lubz: The chairs in a subject cabinet of the Eldenburg-Gymnasium are raised. The state government in Mecklenburg-Vorpommern is sticking to the statewide closures of schools, daycare centers and many businesses. Only from a statewide 7-day incidence value below 100, the Corona protection measures are to be relaxed again. Photo: Jens Buttner/dpa-Zentralbild/ZB

21 April 2021, Mecklenburg-Western Pomerania, Lubz: The chairs in a subject cabinet of the Eldenburg-Gymnasium are raised. The state government in Mecklenburg-Vorpommern is sticking to the statewide closures of schools, daycare centers and many businesses. Only from a statewide 7-day incidence value below 100, the Corona protection measures are to be relaxed again. Photo: Jens Buttner/dpa-Zentralbild/ZB

21 April 2021, Mecklenburg-Western Pomerania, Lubz: The chairs in a subject cabinet of the Eldenburg-Gymnasium are raised. The state government in Mecklenburg-Vorpommern is sticking to the statewide closures of schools, daycare centers and many businesses. Only from a statewide 7-day incidence value below 100, the Corona protection measures are to be relaxed again. Photo: Jens Buttner/dpa-Zentralbild/ZB

21 April 2021, Mecklenburg-Western Pomerania, Lubz: The chairs in a specialist cabinet at the Eldenburg Gymnasium are raised. The state government in Mecklenburg-Vorpommern is sticking to the statewide closures of schools, daycare centers and many businesses. Only from a statewide 7-day incidence value below 100, the Corona protection measures are to be relaxed again. Photo: Jens Buttner/dpa-Zentralbild/ZB

19 April 2021, Baden-Wuerttemberg, Heitersheim: A pupil at the Johanniter secondary school in Heitersheim puts a stick for the Corona self-test into a tube with solution fluid. After more than four months of lockdown, schools were supposed to reopen to all children and young people. But the number of Corona infections in a number of counties is above the threshold of 200 infections per 100,000 inhabitants in seven days, so schools there must remain closed. Other counties are approaching the threshold. Photo: Philipp von Ditfurth/dpa

19 April 2021, Baden-Wuerttemberg, Heitersheim: Corona self-tests from students lie on a table at St. John's Secondary School, along with labeled clothespins. After more than four months of lockdown, schools were supposed to reopen to all children and young people. But Corona infection numbers are above the threshold of 200 infections per 100,000 residents in seven days in a number of counties, forcing schools there to remain closed. Other counties are approaching the threshold. Photo: Philipp von Ditfurth/dpa

19 April 2021, Baden-Wuerttemberg, Heitersheim: A pupil at the Johanniter secondary school in Heitersheim drips ready-made solution liquid for the Corona self-test onto a test strip. After more than four months of lockdown, schools were supposed to reopen to all children and young people. But Corona infection rates in a number of counties are above the threshold of 200 infections per 100,000 residents in seven days, forcing schools there to remain closed. Other counties are approaching the threshold. Photo: Philipp von Ditfurth/dpa

A teacher sorts drawings in an empty classroom at a closed school in Prague, Czech Republic, Wednesday, Oct. 14, 2020. Amid widespread efforts to curb the new wave of coronavirus infections in one of the hardest hit European countries, the Czech Republic closed again all its schools on Wednesday. (AP Photo/Petr David Josek)

A classroom at an elementary school is empty after Israel closed schools ahead of a nationwide lockdown to halt the spread of the coronavirus in Tel Aviv, Israel, Thursday, Sept. 17, 2020. (AP Photo/Sebastian Scheiner)

A classroom at an elementary school is empty after Israel closed schools ahead of a nationwide lockdown to halt the spread of the coronavirus in Tel Aviv, Israel, Thursday, Sept. 17, 2020. (AP Photo/Sebastian Scheiner)

A classroom at an elementary school is empty after Israel closed schools ahead of a nationwide lockdown to halt the spread of the coronavirus in Tel Aviv, Israel, Thursday, Sept. 17, 2020. (AP Photo/Sebastian Scheiner)