PRIMARY school test scores and mock transfer papers must not be used as an 11-plus replacement, principals have warned.
The NAHT union said primary assessments are not comparable across schools.
Following the cancellation of some transfer exams, grammar schools are devising alternative admissions criteria.
There are concerns that some are considering asking for results of in-class tests taken as long ago as P5.
The executive is to meet today to discuss the issue, with education minister Peter Weir under pressure to intervene.
After Covid concerns forced tests postponed until this month to be called off again, the Association for Quality Education (AQE) is seeking to press ahead with a single paper on February 27.
The Post Primary Transfer Consortium has cancelled its assessments.
Ulster Unionist MLA Robbie Butler, a member of the assembly education committee, has offered a potential short-term alternative.
It suggests using two forms of information held by primary schools - standardised assessments and transfer test practice papers.
He said schools could collate and provide AQE candidates with an average score from their best two mock transfer papers.
Mr Butler admitted his idea was not perfect, but said he was trying to start a conversation.
The NAHT said it recognised Mr Butler's effort to help provide a solution "to the shameful position that many of our year seven children have been placed in by the inability of the minister to develop timely contingency planning".
The union said the data that Mr Butler referred to was routinely shared with parents to inform them about progress in learning.
But it warned that primary heads would play no part in anyone's decision to use it "for any other purpose and will not be held accountable for such inappropriate application".
Standardised assessments in English and maths take place every year. However, these are low-stakes and designed simply to support learning and teaching.
Also, due to Covid-19 many schools do not have data from after P5.
Practice papers are used regularly by parents and tutors outside school. However, there is no guarantee of the robustness of any score.
They are carried out at different times in different schools, negating any comparability, the NAHT said.
"While primary school principals will happily supply any standardised assessment data to parents - if they haven't already done so as a matter of course - no primary principal will stand over its appropriateness for this purpose," the union said.
"It rests entirely with the boards of governors of those schools that use academic selection to determine if they can stand over the legalities presented by Mr Butler's proposal. Simply speaking, primary principals will not."
A meeting between ministers to discuss the transfer test will take place today.
Justin McCamphill, NASUWT national official for Northern Ireland, said Mr Weir's responsibilities for exams did not end at GCSE and A-level.
"The minister cannot simply wash his hands of the issue on the basis that the tests are `run by a private organisation'," he said.
"Health and safety must come first; deferring the date of the transfer test is simply deferring the difficult decisions that inevitably will have to be made. It is time for the minister to act and stop the transfer test for this year."
DUP MP Sir Jeffrey Donaldson claimed some parties seemed 100 per cent focused on using the pandemic to advance their objective of undermining academic selection.
"This should not be a debate about selection. It should be about public safety. There is no question of the transfer test going ahead if the public health conditions at that time do not permit it," he said.
"Those who want to use the pandemic to stop academic selection should be honest and outline their real objective is to close grammar schools and stop hiding behind other arguments."
