Both the Tasmanian Association of State School Organisations and the Tasmanian Principals Association said the use of results only as a comparison tool between schools was wrong.

About 25,000 students in years 3, 5, 7, and 9 in Tasmanian schools will sit the National Assessment Program - Literacy and Numeracy testing over three days from Tuesday, May 13, to Thursday, May 15.

Tuesday's test will cover language conventions, Wednesday's reading and Thursday's numeracy.

The state school organisation's president Jenny Eddington said she agreed with NAPLAN results being used in-house by teachers to identify a student's strengths or weaknesses but was opposed to them being made public so people could compare and make judgments about schools.

Mrs Eddington said she thought the Education Department's computer program called the NAPLAN Toolkit, which was rolled out in 2012, was a great tool for teachers as it made it very simple for them to identify exactly what areas a student struggled in, so could focus their learning.

She said she had so far heard no issues around the lead-up to NAPLAN this year.

The principals association president David Raw said he had the impression the department was taking the testing very seriously this year.

He said despite the importance placed on the testing, it wasn't a true measure of where a student was at and people just sought to highlight particular figures and try to compare schools.

Mr Raw said what teachers really cared about was what the student had actually learnt.