"The one thing Catholic schools do really well," he said, "is we get kids to follow instructions."
"So this whole exercise from a public health perspective is having a reasonable set of rules and getting everybody to follow them religiously. Well, that's what we do," he said.
Students wear masks, wash their hands frequently, and stay in cohorts, he explained.
Some of the aging school buildings have large windows that can be opened to improve ventilation. "The fact that we don't have enough money for nice new buildings has turned out to be a huge asset," he said.
Despite the district's large size and student population, Carroll told CNA there have not been differences of spread with regard to the location or demographics of schools. The archdiocese has schools located in both rural and urban communities, as well as in both affluent and disadvantaged areas.
The archdiocese was recently recognized by Gov. Charlie Baker (R) in his State of the Commonwealth address, for safely resuming in-person classes. Carroll said that the low level of infections in his schools helped to sway governmental policy on future school closings.
Initially, when the state designated geographic areas as "red zones" of community spread, Baker wanted the local schools to shut down automatically.
The archdiocese did not close its schools in the "red zones," arguing "that the only safe place for the children in a red zone is a school - a school that's following the (safety) protocols," Carroll recalled.
Carroll said that children in other schools who have had to attend school remotely for months are suffering from it.
"It's going to be catastrophic for these kids, particularly kids from economically disadvantaged backgrounds, homeless kids, kids with special needs," he said.
Despite the low infection level in the current school year, he still acknowledges that new variants of the virus could force schools to close again.
"I think people should reflect on that and they should reflect on the much larger number of people that are being stranded now and how all of their leaders have completely ignored science and health data," he said.
Despite the challenges and new protocols, Carroll said that he was "glad we all got back together," and that he was "astonished" that things are still going well with in-person learning.
"And we're grateful because our kids are doing great," he said.