"... there is no official national tally of school-linked COVID-19 cases, and some states are not reporting how many outbreaks have occurred or how many students and staff members have been infected."

NBC News (17 August), Coronavirus is spreading in schools, but the federal government isn't keeping count:

Coronavirus cases are already surfacing in K-12 schools that have reopened, but the federal government is not tracking these outbreaks, and some states are not publicly reporting them, making it more difficult to determine how the virus is spreading, experts say.
...
“Without good data that tracks cases over time — and shows how one case turns into many cases — there's just no way to answer that question,” said Emily Oster, an economist at Brown University and co-founder of COVID Explained, a team of researchers studying the pandemic. “In January, we'll be in the same position that we are in now, and kids still won't be in school.”