Chicago Public Schools finally released data Friday showing that it considers more than 200 of its schools — almost a third total — to be underused.

But officials changed the way they calculate “space utilization,” leading to confusion among some principals and parents who were unclear about how their schools’ capacity grew since CPS last made the calculations.

That was two years ago, though state law requires the release annually by Dec. 31. CPS spokesman Michael Passman wouldn’t say why they skipped last year but said in a press release the changes “provide a more accurate picture of the state of our schools.” 

Some 229 buildings now are considered underutilized, nearly as many as CPS considers to be efficiently used. That’s according to a newly-revised formula CPS employed to compare numbers of classrooms in a school with the number of students enrolled, calculating approximately 30 kids per classroom.

Another 29 buildings have been deemed overcrowded, including a few selective enrollment schools that can screen applicants and limit who gets in. That leaves 231 “efficient” buildings — now defined as where enrollment constitutes between 70 and 110 percent of a school’s ideal capacity. The efficient range used to be between 80 and 120 percent.

In 2015, just 22 buildings were considered overcrowded.

Taft High School tops the list at 141 percent, followed by Ebinger Elementary, whose parents and elected officials have long begged Chicago Board of Ed members for more space,  at 139 percent. CPS says three high schools — Manley, Douglass and Harper — are under 10 percent.

In the past, schools have been targeted for closing because they were declared underutilized, and some complained they were being unfairly punished for following special education law or for using space to build community.

But some schools saw their capacity rise, though they’d seen no expansions. The principal of National Teachers Academy elementary school, which CPS seeks to turn into a high school, questioned how CPS determined a larger number of classrooms at his school.

Christopher Ball, of the parent group Raise Your Hand, wondered how the system has added room for 6,600 more elementary students since 2015. That’s 172 schools adding seats, 103 losing them and about 100 remaining the same, according to his calculations.

Passman did not respond to messages asking about the discrepancies.

Though CPS is in the last of a five-year moratorium on school closings — imposed after shuttering 50 at once in 2013 for underenrollment — officials are seeking to shut down four Englewood high schools in June they say have too few students to offer a quality high school experience.

Other communities, aware of what district-wide enrollment declines look like in their neighborhoods, are bracing themselves for a possible next round of closings in the next years. High schools especially are wary, though West Side elementary school supporters have already voiced their opposition to more school closings.

The figures were posted to CPS’ website Friday afternoon, when officials are often likely to bury bad news ahead of the weekend. And CPS no longer calculates space use for privately-managed charter or contract schools or for schools serving special populations, such as special education students or incarcerated students.