CHICAGO (AP) — The decision by the Illinois State Board of Education to no longer administer the Partnership for the Achievement of Readiness for College and Careers standardized test to high school students came after the federal government raised concerns.

In a letter obtained by the Chicago Tribune, the U.S. Department of Education determined Illinois violated federal law in the way it administered the test to high school students in 2015 and 2016.

USDE official Ann Whalen noted high school students were “being held to different academic content and achievement standards in reading and language arts, and mathematics … based solely on their zip code.”

The letter indicated the Education Department in April placed Illinois in what the agency calls “high-risk status” for not complying with federal testing requirements.

State Board of Education spokeswoman Megan Griffin told the Tribune the agency has not yet responded to federal concerns and has until Aug. 31 to do so.