Show your work

Late Monday, the city’s Department of Education put out its first-day attendance figure: 82.4%. Tuesday came day two: 84.1%, which Mayor de Blasio Wednesday hailed as “a noticeable and important increase from Monday.” Wednesday, the number rose again to 84.9%, with percentage breakdowns posted by school.

Systemwide attendance should be arrived at via simple math: divide the number of students present on any given day by the number of students enrolled. But officials say they don’t know those two totals yet — so the attendance figure they’re publishing in these early days is instead the total number of kids present among schools reporting data, divided by the number of kids in those schools present plus the number marked absent.

We give the educrats a pass on not knowing total enrollment figures at this point: As in previous years, many families are still making their minds up. And we guess we might even excuse them for having some sizable share of schools lagging in reporting their headcounts (though we’re not sure what’s so hard about knowing the number of kids under one’s roof).

What we just don’t get is why the DOE can’t just report a running total of just how many kids have put their bodies in seats so far, and how many were known to be absent — which is to say, the raw totals informing the percentages they are touting.

This isn’t just a curiosity. As of early this calendar year, when two-thirds of kids were learning remotely, total enrollment stood at about 960,000, about 4% short of the 1.1 million kids educated in the city’s public schools in 2018-19. As the delta variant swirls, de Blasio and Chancellor Meisha Porter have waved off pleas to create a remote option for worried parents.

The public deserves to know the effect all this might be having on the confidence of families who entrust the mayor with their sons and daughters. So, report what we know, when we know it. No more fuzzy math.