As Mayor Rahm Emanuel on Wednesday defended four unpaid furlough days just imposed on Chicago’s public schools, the Chicago Teachers Union announced plans to join national protests against school spending cuts.

CTU officials and members plan to stage walk-ins at schools across the city to lodge their opposition to policies enacted by the mayor, governor and president-elect that they deem harmful.

“Our members and their students and school communities are facing a litany of threats both inside and outside of the classroom,” CTU president Karen Lewis said in a press release. Thursday’s “action is about unity, solidarity and strengthening the bonds that we will all need to overcome challenges from City Hall, Springfield and beyond.”

Unionized charter school teachers also are joining in the protests Thursday, including at Instituto Justice Leadership Academy, 2570 S. Blue Island Ave. There, students, teachers and others — including Ald. Carlos Ramirez-Rosa (35th) and the president of the union of charter school teachers ChiACTS Local 4343 — will hold a news conference and “walk-in.”

Citywide, protesters plan to demand that all CPS schools, including charters, be made into “sanctuary schools,” where undocumented immigrant children won’t face deportation. They also are advocating a tax on the wealthy to increase school funding and protesting billionaire Betsy DeVos, Donald Trump’s pick for U.S. Secretary of Education.

They’re also angry about word that came down suddenly late Friday afternoon that all CPS staffers would face four unpaid furlough days through June.

The surprise announcement was made as top mayoral aides work to ease lingering investor concerns about school and city finances, hoping taxpayers won’t pay the price when Chicago tries Thursday to borrow $1.16 billion by selling general obligation bonds.

Chief Financial Officer Carole Brown’s pitch to investors in Chicago, Boston and New York came after Gov. Bruce Rauner threw Chicago another curve ball.

The Illinois General Assembly approved Mayor Rahm Emanuel’s plan to save two of four city employee pension funds, only to have the governor declare his intention to veto the bill that locked in employee concessions and authorized a five-year ramp to actuarially required funding. Last month, the governor’s veto of a bill giving CPS $215 million in state pension help — aid that already had been built into the school budget — created a potential crisis that could force devastating classroom cuts.

Rauner has maintained he wants to see wider public-pension reform pushed through Springfield before he can help solve City Hall and CPS’ financial crises.

But his actions have heightened concerns among investors that the city is now trying to entice into buying the $1.16 billion in bonds. How the city eases those concerns and insulates itself from the CPS financial crisis will go a long way toward determining the interest rate that must be paid.

On Wednesday, Emanuel was asked why CPS felt the need to order the four furlough days when a $700 million payment to the city teachers’ pension fund isn’t due until June 30. Was it more about appeasing investors and preventing CPS’ dire finances from sparking an interest-rate spike?

“The way to look at this is, if the state had followed through on their commitment to make sure that every teacher, every student and every taxpayer across the state was treated fairly, we wouldn’t be in this situation,” the mayor said after unveiling a new cyber security “boot camp” at Wright College.

For the umpteenth time, Emanuel noted that Chicago taxpayers are forced to “pay twice” — first through their income taxes to bankroll the pensions of suburban and Downstate teachers, and again through their property taxes for the pensions of Chicago teachers.

The state agreed to “finally equalize a decades-old inequity,” only to have Rauner veto the bill to provide CPS with more money, the mayor said.

“That was the wrong choice. And now, we have to look at making some cuts and reforms and things that save money,” Emanuel said.