Extensive connectivity problems on the first day of NAPLAN'S 2019 test schedule plagued hundreds of schools across the country and left many thousands of students unable to complete their exam.

This year 50 per cent of Australian students sat their exams online as part of a three-year transition away from the original written tests.

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Australian Community Media understands Kelso High, Bathurst Public School and Canobolas Rural Technology High School were among the impacted schools.

Central West based NSW Secondary Principals Council deputy president, Craig Petersen, originally praised NAPLAN's move to online but on Friday slammed the bungled tests.

"The credibility of NAPLAN was already under question," he said.

Far from just being an inconvenience, Mr Petersen said it was "distressing" for many students.

"We keep saying it's not a high stakes test, but it is ... there's pressure from media, parents and schools," he said.

"ACARA [Australian Curriculum, Assessment and Reporting Authority] needs to guarantee it will work as it's intended to work."

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In theory the adaptive online testing was a very good idea, Mr Petersen said, however it needed a major overhaul before next year's exams.

"It needs to be tested in a live environment and at a scale, and they need to have a contingency plan in case it goes wrong," he said.

Students who had exams impacted by connectivity issues on May 14 will have the opportunity to re-sit their test on May 28. This is not compulsory.

Meanwhile in Orange, St Mary's Catholic Primary School co-principal Kerry Maher said NAPLAN online was an outstanding success.

"It was absolutely fabulous, we had a really positive experience," she said.

"We had a couple of technical hiccups that were rectified within minutes, we had great technical support.

"We did have extra staff on the ground just in case, but we were thrilled with how it went.

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While students at Macquarie Anglican Grammar School in Dubbo had no issues with their online NAPLAN exams, headmaster Craig Mansour said.

"We staggered it across 10 days and had no more than 55 kids doing it at any one time," he said.

Mr Mansour said the school had minor problems in the online writing test, but those were quickly resolved.

He said it was not fair that the online test went so well for some schools, while others suffered "glitches"

Mr Mansour said if NAPLAN online could be fixed for the future, the faster turnaround in results would mean it could be better used as a diagnostic tool by schools and teachers.

Kelso High, Bathurst Public School and Canobolas Rural Technology High School were contacted for this story but they declined to comment.

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