Chicago Public School principals were being instructed on Wednesday to stop spending money because the broke school district that has already imposed budget cuts, layoffs and unpaid furlough days is running out of cash to make a giant pension payment on June 30.

And warnings to get ready for a “lean July,” the first month of the new fiscal year, left them with many questions about how to plan to open school doors on time in September.

CPS officials told their principals in a webinar that the district was stockpiling remaining cash to make a $688 million pension payment on June 30 — weeks before new property tax revenue was expected to hit CPS bank accounts.

Any expenditures over $5,000 will need the approval of the school’s network chief, the next layer of management above principals. And principals who still needed to buy supplies were encouraged to do so out of federal and state funding sources, rather than money directly from CPS, according to the presentation obtained by the Sun-Times.

CPS had banked on $480 million from Springfield to balance its budget and conceded Wednesday that the money isn’t coming.

“To ensure that we will have enough cash for through year-end, we need your help,” the presentation read.

The district aims to save $45 million total from schools, with each of the geographic-based networks given a savings goal to hit. Principals need higher approval to fill any vacancies, too, the district continued, saying, “please only fill jobs that are absolutely essential for students.”

CPS spokeswoman Emily Bittner characterized the spending freezes as “voluntary,” something several principals contested.

“Principals’ hard work has already prevented significant cuts to the classroom this year, and their voluntary diligence in slowing spending for the remainder of the semester will balance our need to conserve limited resources while educating our children,” Bittner wrote in an email.

She said that network chiefs will work with principals to figure out how much money can remain unspent while purchasing needed items.

CPS told principals to ask themselves if an expenditure is absolutely necessary for children rather than if it is what’s best for children, according to Wendy Katten, of the parents group Raise Your Hand, who spoke to principals about the presentation.

“It’s only going to get worse as decision makers keep ignoring the reality that we can’t cut our way out of this, kids can’t afford to lose anything more in this district,” Katten said. “They’re already not getting basic, core programs and courses in many schools. It’s atrocious, it’s just hideous that kids are bearing the brunt of all of these bad decisions that have been years in the making.”

Raise Your Hand has historically criticized contracts it considers unnecessary as CPS cuts staff, but Katten said funding solutions are more complicated than pointing fingers, and should come from many sources.

One elementary principal who asked not to be named because the principal was not authorized to speak publicly on the issue, said school leaders were given totals to retain in school accounts — for example, $50,000 or $75,000 or $100,000.

Principals squirreled away money all year, the principal continued, expecting that cuts would come mid-year. Through that careful planning, many schools were able to avoid layoffs last month after CPS imposed a nearly 5 percent cut to per-pupil funding. CPS CEO Forrest Claypool, who led the webinar, even applauded their creativity and foresight at a recent Board of Education meeting.

Those same principals now feel foolish for being so frugal because the money the district wants could have been spent on supplies or staff or more services for students, the principal said.

A second elementary principal added that colleagues have not been definitively told whether the savings would be restored once property tax money begins rolling in, or whether the losses would be permanent. So ordering new curriculum at the end of the school year, as many do so supplies will be in place before the first day of classes, might not be possible this spring.

While CPS continues to seek pension help from a deadlocked state legislature, it still hasn’t reached a contract agreement with its teachers union.

Mayor Rahm Emanuel all but urged the Chicago Teachers Union to call off an April 1 “day of action” that threatens to deny Chicago Public School students a day of learning.

CTU President Karen Lewis has not said precisely what the union intends to do on that day, though in flyers and on Facebook, the union called the event “Shut It Down.” It might just be a giant downtown rally to protest several issues: budget cuts, a threatened phase-out of the Board of Education’s 7 percent “pension pick-up” and three unpaid furlough days mandated by Claypool, Emanuel’s handpicked schools chief.

“On April 1, 2016, we are asking all concerned Chicago citizens to unite in a day of action by withholding your labor, withholding your dollars, boycotting classrooms” and a slew of other actions, the CTU wrote on Facebook.

Whatever form that protest ultimately takes, Emanuel argued that it’s ill-advised.

“The adults belong at the negotiating table and our children and our teachers belong in the classroom . . . Kids belong in school learning,” the mayor said.

Last month, the CTU’s 40-person bargaining unit unanimously rejected a new four-year contract that would have given teachers small annual pay raises, capped the number of charter schools at 130 and ruled out economic layoffs in exchange for teachers picking up their full, 9 percent pension payments.

Lewis recommended the contract but was unable to deliver the approval of her members because of what she called a “lack of trust in CPS” and what she called the district’s “weasel language” in previous contract talks.