During the monthly “Ask the Mayor” segment on GBH’s “Boston Public Radio” on Tuesday morning, a caller from South Boston raised what seemed like a startling statistic.

COVID-19 cases in Boston schools appeared to be over 600 percent higher in the first month of school this year, compared to the same time last year.

Indeed on paper and at first glance, data reviewed by Boston.com shows after the first five weeks of school this year, there were 1,426 cases reported among students and teachers, up from the 219 total cases reported in the first five weeks of last school year.

But the data, in reality, is simply not that cut and dry, according to Boston Public Schools.

“Here at Boston Public Schools, student safety is our highest priority,” a district spokesperson said in an emailed statement Friday. “Every year, as we continue to learn more about COVID-19 and how it affects our students and families, we adjust our testing policies and protocols to reflect that and maintain the highest level of safety possible. Comparing this year to last is like comparing apples to oranges: our approach has improved to meet the needs of our communities.”

The district says an internal measurement shows the number of COVID cases among students and teachers is actually similar to last fall.

And there are a few reasons for that, especially changes in the district’s testing policy this fall compared to last fall.

This school year marks the first to start during the pandemic where students are no longer required to continuously wear masks and are not mandated to regularly test for the virus as they did last school year. Instead, Boston schools say masks are “optional but recommended,” except in certain situations when they are required, namely if there is a classroom-wide or school-wide outbreak.

Masks are also required in all school health offices; if a student or staff member feels ill or is showing symptoms; in cases where a student or staffer is exposed to someone who tested positive for the virus; and when students or staff members are returning to school from isolation within 10 days after their first positive test.

For testing, all staffers and students are given one at-home rapid antigen test kit every two weeks, with each kit containing two tests. There is no rule requiring those tests be taken, but the district said personnel and students are “strongly encouraged” to test each Sunday night or Monday morning.

Those who show symptoms of COVID-19 or are known or suspected to have been exposed to the virus are required to test, however. Students and staff who exhibit symptoms of the virus can be tested in school, but students’ parents must provide consent.

“There have already been instances here where a cluster has started to show signs of appearing in a school and that school had masking in place just to respond and make sure that could be kept under control,” Wu said Tuesday on GBH. “So that is the policy for now — that we’re monitoring things very closely and have an approach based on individual schools and the situation in real time.”

Data from early in the 2021-2022 school year came as BPS relied on state-sponsored pooled testing, a program that ended earlier this year, according to the district. Students needed parental consent to participate in that testing model, and the district largely did not receive consent forms from families until later in the fall or around November and December, BPS said.

This year, although weekly testing is voluntary, BPS students are testing more frequently at the onset of the school year than this time in 2021, which the district said contributes to the higher number of cases reported. Students, notably, also do not need consent forms to use the antigen test kits. But for symptomatic testing, which requires consent from parents, the district has received consent from families much earlier this school year than last year, too, according to the district.

In a pandemic filled with data points, the metric BPS watches closely is a percentage derived from the number of positive test results among students and teachers at a school divided by the total of the student body and staff. Those percentages collected during this school year are so far similar to last school year, according to BPS, which communicates daily with the Boston Public Health Commission about COVID data.

Heading into another pandemic fall, Boston has seen a recent uptick in COVID-19 concentration in local wastewater, with the amount of virus detected in the sewage having jumped 99.9% over the two weeks ahead of Oct. 7.

The rise prompted city public health leaders to issue a renewed call for residents to take precautions to help mitigate virus spread, including through booster vaccinations, testing regularly for COVID, and isolating in the event of a positive test.

Compared to last fall, there is also a different dominant strain of the virus in the United States. The BA.5 omicron variant, is highly contagious.

Dr. David Hamer, a professor of global health and medicine at Boston University and an attending physician in infectious diseases at Boston Medical Center, said the variant, like others, does not pose a significant health risk to children, so long as they do not have any underlying illnesses.

But infected kids can still exacerbate community transmission.

“They have very mild illness and yet they can shed a lot of virus,” Hamer said.

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