BERLIN -- Masks during class, masks only in the halls, no masks at all. Distance when possible, no distance within same-grade groups, no distance at all.
As Germany's 16 states start sending millions of children back to school in the middle of the coronavirus pandemic, the country's famous sense of "Ordnung," or order, has given way to uncertainty, with a hodgepodge of regional regulations that officials acknowledge may not work.
"There can't and never will be 100% certainty," said Torsten Kuehne, the official in charge of schools in Pankow, Berlin's most populous district, where 45,000 students go back to school today. "We are trying to minimize the risk as much as possible."
Germany has won plaudits for managing to slow the spread of the coronavirus quickly, efficiently and early, but the opening of schools is proving a new challenge as the country struggles to balance the concerns of anxious parents and children, skeptical scientists, worried teachers and overtaxed administrators.
Many around the world will be closely observing the real-life experiment offered in Germany to see what works and what doesn't.
The U.N. has said as many as 100 countries have yet to announce a date for schools to reopen, and Secretary-General Antonio Guterres warned of a possible "generational catastrophe" in education. He urged that restarting school be made a "top priority" once countries have the coronavirus under control.
Germany has seen more than 217,000 confirmed cases and about 9,200 deaths, and it brought down a peak of some 6,000 new daily infections in March to the low hundreds. Numbers have been creeping back up, however, and topped the 1,000-per-day mark in recent days for the first time in about three months.
Israel attempted a full reopening in May, at a time when the coronavirus was widely thought to have been beaten in the country, only to suffer new outbreaks that led to schools being shut down again and a surge in the spread of the virus nationwide. In South Africa, four grade levels were restarted in June but then closed back down when the country's virus cases surged.
As Berlin sends its nearly half-million students back to school, many fear something similar could happen.
"The concerns are enormous because the schools are hot spots," said Doreen Siebernik, who heads the Berlin branch of the GEW teachers union. "I know that there are pupils coming to school who have contact with hundreds, with thousands of people every day."
Berlin's back-to-school guidelines are middle-of-the-road among German states. Federal Health Minister Jens Spahn said Germany's staggered returns and different approaches will help determine what works and what doesn't.
Berlin's plan includes requiring students and teachers to wear masks in hallways, but not during instruction or on the playground. Sports, music and drama will be allowed, but with restrictions, like requiring choir members to keep their distance from one another.
Berlin's minister for education, Sandra Scheeres, said "it's not possible in a school" to always keep students safely away from one another, but that the effort should be made. Students are to be kept in "cohorts" -- groups that should not mix -- so that if there is an outbreak, only those affected would need to be quarantined.
The state government recommends those groups don't mingle outside school either, but it was not clear how that could be enforced.
"There are conflicting priorities -- health protection on the one hand, which is very important to us, and on the other hand that we want to ensure the right to education of every single child," Scheeres said.
A Berlin Institute of Technology study on coronavirus transmission concluded that classrooms should be ventilated for a full 15 minutes every half-hour. Scheeres' current plan calls for windows to be opened after each 45-minute class.
Dr. Isabella Eckerle, head of the emerging viruses research group at the University of Geneva, said there is still a lot to learn about how children are affected by the coronavirus and transmit it, but that it was clear from school openings in other countries that they could spark wider outbreaks.
"If we go back to the normal school day now, clinging to wishful thinking that children do not play a role in the pandemic, that will come back to haunt us," she said. "Instead of ideologically charged discussions, we need pragmatic concepts to get us through the winter."
Marco Fechner, a father of two and parent representative in the Pankow district, noted in a sharply worded open letter to Scheeres and the city's mayor that many classroom windows don't open, and that the government has stricter mask rules for supermarkets and its own offices than schools.
He urged the administration to focus more resources to permit some learning from home so that class sizes and contact could be kept to a minimum.
"This decision is absolutely incomprehensible to me as a father, and I fear for the health of my children and our relatives," Fechner wrote.
Information for this article was contributed by Josef Federman, Jill Lawless, Mogomotsi Magome, Dorothee Thiesing, Frank Jordans and Kirsten Grieshaber of The Associated Press.