About 4,000 Northern Territory students have had their NAPLAN results regraded, following a glitch in the Education Department's marking system.

The Territory Government says a processing error meant some answers in last year's tests were not correctly counted.

Education Minister John Elferink says the error has been rectified and a more stringent marking process will be put in place.

"Some of those 4,000 students will see a very small increase in their overall results," he said.

"While we are not happy that this has occurred, once I was advised ... I immediately insisted that all affected parents be contacted and all affected students, of course, as well as making public this incident.

"It doesn't have a major effect on the final results, but what it does do is paint a less than completely accurate picture for some students and parents.

"We are anxious to have that corrected as a matter as professionalism."