Thousands of high school students across the Thames Valley District School Board couldn't write the Education Quality and Accountability Office (EQAO) test Thursday.

Widespread technical issues across the province forced Ontario's EQAO to pull the plug on an online voluntary literacy test for high school students.

Shortly after the test got underway, the agency posted a tweet saying the test was being cancelled due to technical issues and apologized to participating schools and students for the failure.

The voluntary test was meant to serve as a trial of the technical readiness of the EQAO and the schools to support online assessments, and a "risk-free" way for students to take it ahead of the next scheduled assessment in March 2017.

If students passed the online test, it would count, but if they failed or didn't complete it, they would be considered "first-time eligible" for the test next spring.

The program was open to all 72 school boards, as well as First Nations and private schools.

"We recognize all of the work that schools have done to prepare for this trial," the agency said in a tweet. "We are disappointed at the outcome of this trial and sincerely apologize for this development."

Other boards across the province were also affected, including the Avon Maitland District School Board, Grand Erie School Board and the Greater Essex County District School Board, among others.

With files from The Canadian Press.