Chicago Public Schools have postponed high school admissions tests scheduled this weekend as the private testing platform that administers the exam continues to experience technical difficulties.

The platform operated by a private vendor crashed Wednesday when up to 24,000 CPS eighth graders were taking the exam that’s part of the process of getting into one of the city’s elite selective enrollment high schools.

Kids who don’t attend CPS for eighth grade were set to test this Saturday and Sunday. And after initially saying those exams would go on as planned, district officials said Thursday that the technical problems have not been resolved and testing would be postponed “in order to ensure a smooth testing experience.”

“We are working now to reschedule all students who were scheduled to test this weekend and will share updates to families as soon as possible,” CPS spokeswoman Samantha Hart said in a statement.

The school system has a $1.2 million contract with Riverside Assessments LLC, an Itasca-based company, to administer selective-enrollment tests.

Maria Bradley, a spokeswoman for Riverside Assessments, said the company “is committed to the best possible student testing experience, and everyone across the entire company is engaged in resolving this issue.”

The test is part of an often-cumbersome and stressful high school admissions process that has been likened to college admissions. CPS shortened the test to an hour this year, along with other changes, to help “reduce anxiety for students.”