Thousands of Ontario high-school students were caught off guard on Thursday by technical issues that scuttled plans to take an online literacy test.

The Grade 10 literacy assessment, usually conducted in the spring, was to be made available online for the first time to as many as 190,000 students at more than 900 secondary schools.

The students had volunteered to test the online version before it was to be rolled out further.

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But plans changed on Thursday morning because of technical problems and, by the end of the day, the provincial agency that administers the test cancelled it.

"We regret to inform you that we have cancelled today's assessment," the Education Quality and Accountability Office tweeted. "We recognize all the work that schools have done to prepare for this trial."

Education Minister Mitzie Hunter said officials are trying to figure out what caused the widespread technical problems.

Ms. Hunter said she is disappointed by the cancellation; students had been prepared to write the test but could not.

Ryan Bird, a spokesman for the Toronto District School Board, said officials are still assessing how widespread the problem was in the city's schools. "Some students were able to finish it, others were in the middle of it, while others didn't get a chance to start it," he said.

Ryan Reyes, a spokesman for the Peel District School Board, said students will not be penalized if they were not able to complete the test. A paper and online version will be available in March, he said. "Affected families will receive communication from the school with further details."

With a report from The Canadian Press