Schools across Australia have been told to “pause” Naplan testing for more than a million primary and secondary students on its first day after widespread technology problems with its online platform.

In a statement on Wednesday morning, the Australian Curriculum, Assessment and Reporting Authority (Acara) said it was “aware of a widespread issue affecting students being able to log on to the online platform to complete their Naplan assessments”.

“This issue is being urgently investigated by our technology provider, Education Services Australia, who run the platform,” it said. “Schools have been advised to pause testing while this is being investigated.”

Acara said schools were being provided with support and advice to minimise impacts on students.

About 1.4 million students are expected to complete this year’s Naplan tests, which transitioned to fully online in 2022 after trials away from paper began in 2016. Year 3 writing tests are still completed on paper.

In 2019 Naplan test computer glitches prompted the Victorian government to allow schools to return to pen-and-paper assessments.

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Late on Tuesday morning, multiple schools posted to social media advising parents and carers that the tests would be delayed as a result of the outages.

Erskine Park high school in western Sydney said on Facebook: “Due to technical issues with the Naplan online server, a number of schools, including ours, were unable to access Naplan today. An updated timeline will be shared.”

Rooty Hill public school in western Sydney said it would be postponing Naplan assessments until Wednesday due to the “statewide” issues.

The New South Wales Education Standards Authority, which is responsible for administering Naplan in the state, said Acara had reported that “some schools are experiencing slowness in the platform” and it was investigating the delays.

“ACARA advises to continue with open tests, if able, but do not start new tests. Principals and NAPLAN coordinators will be emailed further information,” it said.

Before the tests began, parents were sent a 35-page guide to installing a locked-down browser for assessments, which prevents students from using other applications or websites during testing.

The document said the browser would be installed by the school technical support officer. But students with their own devices would need help to set up their device for assessments.

According to reports on social media, an error reading “communication to the server has been lost” was displayed on the screens of students during tests.