Oklahoma's public schools superintendent suspended online testing across the state on Monday after middle and high school students systemwide experienced disruptions during high-stakes standardized tests for the second consecutive year.

Superintendent Janet Barresi directed testing vendor CTB/McGraw-Hill to suspend testing after about 8,100 Oklahoma students experienced problems such as computers moving very slowly or freezing altogether. The disruptions affected students taking high school end-of-instruction exams and those taking tests in grades six through eight.

A similar glitch stalled testing last year in Oklahoma, as well as in Indiana, Kentucky and Minnesota. Of those, Indiana also used CTB/McGraw-Hill as its testing vendor.

"It is an understatement to say that I am frustrated with McGraw-Hill," Barresi said. "It is an understatement, actually, to say that I am outraged."

CTB/McGraw Hill issued a statement Monday evening apologizing for the disruption and saying that a "network service interruption" affected some schools and that the problem was found and corrected within three hours.

"We worked with our technology vendor to isolate and correct the troubled network electronics," according to the statement from company spokesman Brian Belardi.

"We note that today's event is unrelated to the capacity of CTB's IT infrastructure, which has been greatly enhanced since 2013," the statement said.

Despite last year's problems, Barresi said the state renewed its contract with the company for more than $13 million this year in large part because there was not enough time to solicit bids and select another vendor before the tests were to be administered this spring.

"We looked at it and realized there was simply no time ... to get that done and to be able to put out an assessment for this year," Barresi said.

Barresi said that technicians from the company were on site working to determine the exact nature of the problem. She also said that Oklahoma had taken numerous steps to ensure the state was prepared, including extra training and conducting "stress tests" specifically to safeguard against any problems.

"This appears to be 100 percent a failing of CTB," Barresi said.

In Norman, a suburb about 20 miles south of Oklahoma City, more than 1,100 middle and high school students were scheduled for testing on Monday, and rescheduling will pose major problems to students, teachers and parents, said Shelly Hickman, a spokeswoman for the district.

"When you have disruptions of this magnitude, it's a big deal," Hickman said. "It impacts the students' mindset. It's a huge disruption to them, and it impacts their performance."

Especially in larger school districts, comprehensive schedules are developed to test certain students on specific days, coordinate volunteer monitors and notify parents.

"You have to reshift the entire schedule," Hickman said.

Students in grades three through five, who take paper-and-pencil tests, were not affected, Barresi said.

After last year's testing problems, Oklahoma reached a settlement agreement with CTB/McGraw-Hill for more than $1.2 million in damages, including a $367,000 cash settlement that was disbursed directly to districts. The money was also used for additional training for teachers and to conduct a study on the impact of the disruptions on student test scores.