Amid all the pain and disruption, a year of coronavirus has given Americans a new respect for those working to keep daily life as normal as possible, from the frontline nurse to the Amazon delivery man. Near the top of this honor roll is an especially unsung hero: the Catholic-school teacher. The National Catholic Education Association reports that its schools boast a total enrollment of 1,626,291. In ordinary times their teachers do an extraordinary job, especially for their poor and minority students. As Justice Sonia Sotomayor once said, “Catholic schools have been a pipeline to opportunity” for people like her—poor, Latina, raised by a single mom. Since the Covid-19 outbreak, Catholic-school administrators have moved heaven and earth to keep their classrooms open to new generations of Sotomayors. “The science is clear that there is no substitute for in-person learning, especially for poor and minority children most at danger of falling behind,” says Tom Carroll, superintendent of Catholic schools for the Archdiocese of Boston. “Across the nation, the Catholic school approach is to stay open wherever we are allowed.” It’s been a roller coaster. During the first days of the lockdowns, many Catholic schools closed forever because of a cash crunch. Kathy Mears, the NCEA’s interim president and CEO, reckons that Covid forced the closure of 107 Catholic schools, though an exact number is difficult because in many cases other factors were also involved. But a funny thing happened after the shutdowns. Once moms and dads realized that the Catholic schools left standing were staying open through the pandemic, they began moving children out of public school. It’s not been enough to stave off the 6.4% drop in national enrollment the Catholic schools have seen since Covid-19 hit, but it does highlight that these schools are among the few real alternatives parents have today. “I can date the change in Massachusetts,” says Mr. Carroll. “We were facing a drop of more than 5,000 students. But when the three teachers unions in the state announced they wanted a delayed opening and remote learning, our phones started ringing off the hook.” Alas, not everyone can afford the Catholic option even though the tuitions they charge are relatively modest. Just as significant, Catholic schools prove you can keep classrooms open while keeping Covid-19 at bay, which gave teachers unions another reason to resent them. The good news is that Covid-19 has heightened awareness that too many kids are held in education limbo by public-school systems that cannot put their students first because they are hostage to the unions. Take the three largest public-school systems. In New York, Catholic schools have been operating safely since the fall, while the teachers unions continue to fight returning to the classroom. Mayor Bill de Blasio’s latest is that he doesn’t plan to reopen public schools fully until September. Ditto for Chicago. Here again students are back in their Catholic schools. But public school parents are out of luck: The Chicago Teachers Union has defied orders to return to class. Los Angeles is home to the nation’s largest Catholic school system, with more than 70,000 students—78% of them children of color. Its situation is different because Gov. Gavin Newsom’s restrictions on school openings also apply to religious schools. But some Catholic schools have received waivers, and as soon as case rates fall below the state restrictions, almost all plan to reopen immediately. This happens to be National Catholic Schools Week, and it will be illuminating to see if America’s most prominent Catholic school alumnus—President Joe Biden —even acknowledges them. We know he’s grateful: While chatting with students during a 2013 visit to his alma mater, Archmere Academy in Wilmington, Del., he credited the school with making him the man he is today. With the help of Archmere’s priests and nuns, he said, he overcame a stutter that had left him with cruel nicknames such as “Joe Impedimenta.” “I owe Archmere so much,” he told the students. During the pandemic, America’s Catholic schools are providing a similar lifeline to hundreds of thousands of children who would otherwise be out of class and losing ground. The president has never fought for school choice, but in 1997 then-Sen. Biden did declare on the floor that the plight of children “presently caught in a failed public school” was leading him to rethink his opposition to vouchers. Perhaps now, with so many public-school systems leaving their students in the lurch, would be a good moment for another reconsideration. Don’t parents deserve the option of a school that will put their children first, just as Mr. Biden’s did? “It’s wonderful that President Biden appreciates what his Catholic alma mater did for him,” says Jeanne Allen of the Center for Education Reform. “But the test will be whether the president will support efforts to ensure that poor and working-class kids just like him have the same life-defining opportunity he had.” Write to mcgurn@wsj.com.