An official inquiry will look at technical issues plaguing the NAPLAN school tests.

When the tests were launched nationwide in mid-May, some students had serious connectivity issues while others were unable to log in at all.

Re-sits start this week, with over 1800 students in Queensland and children at 400 schools in NSW expected to do so.

The Australian Curriculum, Assessment in Reporting Authority (ACARA) manages the tests, and says re-sitting them is optional.

Queensland's education minister says full implementation of NAPLAN online should be delayed beyond its planned 2020 start.

Education Minister Dan Tehan says all state and territory ministers agreed to move from pen and paper to online delivery of NAPLAN tests in 2014.

Mr Tehan has ordered an independent review in coming weeks to look at what went wrong with the online tests.

The online tests are adaptive, meaning each question can change based on the last. The system is expected to help reveal the specific areas where individual students struggle or do well.