“At some point, you have to make those decisions on the basis of a cost-benefit analysis: What are the costs of not reopening schools, what are the benefits with regards to the virus for not reopening schools,” the Republican senator said during a CNBC interview. “I think in the short and long term, the costs are extraordinary.”

Rubio’s comments followed a week filled with debate over how and when schools should reopen. After schools across the country shut down in the spring to prevent further spread of the virus, many governors have expressed hesitancy about reopening schools as case numbers rise in multiple states. As California, Texas, Arizona and other states reported record highs in new case numbers, the U.S. as a whole has recently set records in new cases, with more than 3.3 million reported nationwide on July 13, according to a Johns Hopkins University tracker.

Florida, which was one of the first states to reopen, has experienced rising case numbers for several weeks in a row. On Sunday, health officials reported the state’s highest single-day increase yet, 15,300 new cases, which broke the nation’s previous single-day record that New York set in April.

Despite the rising case numbers, President Donald Trump and his administration last week expressed their determination to have schools resume in-person instruction by the fall semester. Though the president’s critics were quick to condemn his call for schools to reopen regardless of the threats still posed by the virus, Trump and Education Secretary Betsy DeVos have noted the costs to children who are unable to learn and socialize in classrooms alongside their peers. As an added incentive for schools to comply with the administration’s recommendations, both Trump and DeVos said they were considering blocking federal funding for those that postponed reopening.

Rubio said Florida counties that have not seen as great a surge in new cases may be ready to reopen their schools sooner than others. Harder-hit counties may require additional measures to ensure that schools can reopen safely, he said.

“It isn’t going to be school the way we’re used to in normal times,” he told CNBC. Even so, he said some costs—like learning losses among children and keeping adult workers home to care for kids who are unable to return to school—could be worth the risks of reopening.

“What is a parent who’s being required to go to work supposed to do with a 9-year-old—leave them at home all day in front of a computer to do schoolwork? It’s just not feasible,” Rubio said. “We’re going to have to figure out a way to [reopen] in the safest way possible.”

Angela Morabito, the press secretary at the U.S. Department of Education, told Newsweek that all schools will be required to provide students with “fully operational” environments in which to conduct their studies but said the form those environments take may be different from one school to the next.

“Secretary [DeVos] has been clear that all students must be learning and all schools must be fully operational in the fall. It’s not a question of ‘if,’ it’s a question of ‘how.’ That does not mean one-size-fits-all,” Morabito said.

“Students and families need options based on their personal situations and the local health realities. Schools should continue to rethink their approach to education to be more student-centric and deliver a more personalized education. Schools could choose to adopt a hybrid model as one option for students, but every student needs to have access to [a] learning environment that is fully operational and that provides the student a full school year of learning starting this fall,” Morabito said.

According to the Centers for Disease Control and Prevention, children under 18 account for only 2 percent of the coronavirus cases reported throughout the U.S. and do not account for a significant percentage of seriously ill COVID-19 patients. But health officials have warned that children can be infected with the virus without experiencing any symptoms and could pose threats to their parents, grandparents and other adults with whom they interact.

Though Rubio did not address asymptomatic infections specifically in connection with the school reopening discussion, he did say young people spreading the virus unknowingly were likely a significant factor in the new cases reported in Florida and other states seeing surges.

“When you’re in close contact indoors with someone who’s infected, they’re going to infect you,” Rubio said. “Neither one of you may have symptoms, but both of you may go home and infect your parents or grandparents in another setting, and that’s where it becomes a problem.”

The senator also acknowledged that the virus remains a considerable threat to Americans’ health and economic well-being.

“This is going to be a challenge we’re going to face for the foreseeable future,” he said. “We’re going to have to do the best we can to mitigate risk and protect the most vulnerable.”

This story has been updated with a response from Angela Morabito, the press secretary for the U.S. Department of Education.