Gov. Bruce Rauner did on Tuesday what he’s been vowing to do for months: nix parts of a new bipartisan school funding bill he didn’t like.

But Rauner’s changes didn’t just target the “Chicago bailout” he’s been railing against since the legislation passed in May. Experts say his long list of line-by-line changes to Senate Bill 1 would affect a lot of districts in Illinois, reputed as the worst in the country for funding for poor students.

The Illinois General Assembly now has 15 days to take up the amendatory veto — with the clock beginning on Wednesday since the Illinois Senate procedurally read in the veto on Tuesday. That means a veto could happen the week of some traditional events at the Illinois State Fair, when many lawmakers will be in Springfield.

Meanwhile, the clock is ticking for Illinois’ public schools, most of which are counting on their first slice of their shared $6.7 billion in general state aid payments due on August 10, to be able to open their doors. Except the Illinois State Board of Education can’t allocate or dispatch any of that money without the new funding mechanism. Democrats in June included a provision in a budget bill that held up school aid payments without the passage of an “evidence-based” school funding formula — in an effort to get the governor to support the very measure he vetoed on Tuesday.

It all wound up leaving plenty of unanswered questions.

Will CPS and other schools throughout the state open on time?

CPS leaders, including the mayor, have vowed to do “whatever’s necessary” to open Chicago Public Schools on time — but for CPS, that’s after Labor Day. Lots of Chicago’s charter schools start classes in August, but they’re set to open on time, according to the Illinois Network of Charter Schools.

Districts outside of Chicago, some of which have started as of Tuesday, have warned they may not be able to open — or won’t stay open long. They’re “crisis planning” now, said Ginger Ostro, head of Advance Illinois, which has championed a new funding formula. The Illinois State Board of Education says it needs the formula “in early August” to get those payments processed on time. The board can and will, meanwhile, dispatch another $5.2 billion in federal and other state money.

How much money does CPS lose under the Rauner veto?

It’s hard to say, since Rauner’s veto takes big bites out of Chicago — by eliminating the block grant — and several smaller bites, too. Chicago officials said they couldn’t readily calculate a total but said CPS’ block grant was about $250 million this year. Rauner is willing for the state to start paying CPS’ normal pension costs —$221 million this year — if the payment can move from SB1 to the pension code. There remains a question of whether the state constitution would permit that.

The Rauner administration has published data on a state website showing that CPS will receive $145 million less under the veto that it would have received in the original bill. But those numbers, too, are a bit shaky. The administration sent the veto to the state board for an analysis – and the figures Rauner had been citing are no longer available without a username or password. The governor’s office said it would be updated when the board releases its analysis, but didn’t explain why the figures are no longer publically available.

What about other school districts?

The Rauner administration figures show they gain as CPS’ block grant gets redistributed. But according to Advance Illinois, strong advocates of the evidence-based model used in SB1, districts outside of Chicago would not be immune from Rauner’s changes.

“The veto punishes all districts by putting a cap on regional costs, ignoring inflation, and removing protections for districts in the future in the event that local resources are used to pay for pensions,” according to Advance.

For example, changing a provision in 2020 from holding each district harmless overall to holding it harmless on a per-pupil rate would affect the hundreds of Illinois districts losing students, and that’s problematic, Ostro said, because the state’s funding already is too low.

“Under the SB 1 model no district loses money year over year — it’s about how new dollars are distributed,” she said. “That’s important when districts are already inadequately funded.”

What happens next?

Rauner’s amendatory veto puts the entire school funding formula in limbo. The path to movement on an amendatory veto is fairly shaky. Legislators can vote to approve the changes, which is unlikely with a Democratic majority. They can also neglect to do anything about the veto, which will kill the measure completely. If the Illinois Senate can round up Republican support for a supermajority to override the veto, it must also pass the same muster in the Illinois House — where Illinois House Speaker Michael Madigan has accused Rauner of “choosing crisis over compromise.”

Targeting Chicago as being treated differently when it comes to school funding is traditionally used as a talking point to continue negotiations, according to a top Republican. But the governor on Tuesday signaled other issues he supports which weren’t included in the veto, including a private school scholarship program that includes tax credits. The Republican source noted it’s unusual to issue an amendatory veto while still vouching for additional measures he supports.