CHICAGO – Chicago Public Schools’ decision to administer new Common Core student tests to only about 10 percent of the city’s 600 schools could cost the state over $1 billion in federal aid.

In a recent letter to Illinois Schools Superintendent Christopher Koch from assistant U.S. education secretary Deborah Delisle made it clear the state could lose as much as $1.17 billion in federal education funding next year if Chicago schools don’t comply with Common Core testing requirements, Crain’s Chicago Business reports.

That money represents about 84 percent of the state’s federal aid for education, and about one in ten dollars spent by Illinois schools, according to the news site.

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Koch previously wrote to U.S. Education Secretary Arne Duncan to request a year delay in administering Common Core exams, known as the Partnership for Assessment of Readiness for College and Careers test, because of Chicago’s decision not to fully implement the test.

But the letter from Delisle makes it clear that’s not an option, unless the state is willing to forego the federal funds.

“Politically, the problem is that, given national wrangling over school standards, Duncan cannot be seen as being easy on Chicago, said one source close to the center of the flap. That doesn’t mean Illinois would lose all of the money, but a sizable hit is likely,” Crain’s reports.

“The matter was discussed at length at last week’s state board meeting, and it’s being discussed today by officials at the Chicago Board of Education, which so far has backed the limited-test decision by (Chicago) Superintendent Barbara Byrd-Bennett.”

Neither Duncan nor Byrd-Bennett responded to Crain’s request for comment.

The PARCC testing is among myriad of issues Common Core opponents have raised with the new national learning standards. Other issues include the loss of local control for public schools, a lack of academic rigor, the expense of technology and other upgrades necessary to administer tests online, and concerns about massive student data collection that’s forwarded to the government as part of Common Core.

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Rev. James Meeks, the new chairman of the Illinois state school board, told Crain’s state officials “are greatly concerned” about the impact Chicago’s limited testing decision could have on funding for students statewide.

“We are working through the process” in hopes to avoid financial penalties, he said.

Some who commented on the news online pointed to the Chicago Teachers Union – an outspoken opponent of Common Core tests – as the main culprit behind the limited-testing decision and the potential loss of federal funds.

“The teachers union doesn’t want standardized tests because the low and non improving scores will be shown and expose the bad job the teachers are doing,” Jeff S. posted. “They would basically throw the kids under the bus and give up billions in funding to protect their own political interests.”

Others theorized that the decision is being driven by the city’s school choice proponents.

“Jeff, I think you will see over time it is not the CTU behind this. There is a very real concern the tests will show nominal improvement or a decline in performance by charter schools versus traditional CPS schools,” dave_hanna posted.

“The charter community feels another year will provide a truer picture of their effectiveness. With the amount of time, political capital and money CPS management has invested in the charters, along with the growing impression the school closings have not moved the dial on the performance of those many affected students, CPS has much riding on testing benchmarks being up, not down.”