Thousands of children in northern Germany became the first in Europe to begin a new school year today after months of curtailed hours over the coronavirus pandemic.
Education ministers across Germany's 16 states had agreed for schools to reopen full-time after the summer break.
In Mecklenburg-Western Pomerania, the first state to restart full-time classes, 150,000 pupils returned to their classrooms.
With children in Hamburg to also return to school later this week and Berlin to follow next week, a debate is now growing over whether full-time school is realistic as infection numbers rise in Germany above 500 per day again.
But officials warn that children cannot afford to miss more school.
"The children need to be present in school because we have to prevent more lost time," Steffen Kaestner, headteacher of the CJD Jugenddorf-Christophorus school in Rostock, told AFP.
Masks must be worn in the corridors, classrooms are regularly ventilated and pupils are urged to wash their hands regularly and respect social distancing.
Not all went entirely to plan this morning, however, as students excited to see their friends again after so long could not resist a few hugs in the playground.
"We hope everything will go well. We just don't know where they have been on holiday," Mr Kaestner confessed.
CJD has 1,350 students aged 9-18. Only two are missing, a decision by their parents, "who belong to a risk group," said the headteacher, but all the teachers are present.
Mecklenburg-Western Pomerania has so far been relatively unaffected by the coronavirus, with only 20 deaths out of a total 9,200 in Germany since the beginning of the crisis.
"Of course we are aware of the danger, but we have very few new infections in our region," said Kay Czerwinski, a member of a local parents' association.
"The most important thing is to go back to school and avoid falling further behind, otherwise we risk having a lost generation," he told AFP.
Masks have so far not been made compulsory in schools in the region, but the state's health minister Bettina Martin told a local radio station that she wanted to "play it safe" and require masks outside of classrooms.
Government spokeswoman Ulrike Demmer also came out in favour of masks today, telling a press conference the measure "sounds like a reasonable consideration".
Other regions have already decided on compulsory masks in schools. In Berlin, where school starts on 10 August, pupils and teachers will have to wear them in all parts of the school apart from classrooms and playgrounds.
The same is true in Bavaria, where masks may even become compulsory in class, depending on the regional spread of the pandemic.
But Heinz-Peter Meidinger, head of the DPhV teachers' union, fears "enormous chaos" because of a "lack of preparation" in schools.
"In many schools, ventilation concepts and the isolation of learning groups cannot be implemented," said Mr Meidinger, who instead favours alternating face-to-face and distance learning classes.
Some classes also cannot be taught because the teachers belong to a risk group. The DPhV has identified some 400 such classes in Mecklenburg-Western Pomerania alone.
Faced with all these difficulties, it would be "illusory" to think that schools "will return to normal functioning", warned Saskia Esken, co-leader of the Social Democrats, the minority coalition partner in Angela Merkel's government.