LAWS that allow schools to discriminate on the grounds of religion when appointing teachers must be scrapped, a conference will hear.
The NASUWT will today call for changes to legislation at its annual national conference.
It wants an overhaul of the Fair Employment and Treatment Order (FETO) to remove the exception regarding the employment of teachers.
This allows schools to use religious belief as a ground on which to discriminate between candidates for posts.
It has been justified because all grant-aided schools are required by law to provide a daily act of collective worship and religious education in line with a specified Christian core syllabus.
Those employed to teach religion in a school under Catholic management must be able to demonstrate they have the capacity to do so in line with its ethos.
Unlike subject-specific teachers in post-primary schools, primary staff are ‘generalists’ required to teach across the full curriculum - it follows that they must teach religion.
The issue has been the subject of significant political debate, as well as investigation by the Equality Commission.
It was also the focus of a paper from the Transforming Education Project at Ulster University, which said in a post-conflict, increasingly multi-cultural society the exception was "something of an anachronism".
It noted that it did not work in isolation, however. Teacher mobility between traditional sectors was also inextricably connected with both the separation of teacher education institutions and policy
concerning the place of religion in schools. In order to ensure equality of opportunity for all teachers, it said, these connected issues also required attention.
However, it said repealing the teacher exception to FETO would be a "hugely symbolic first step in tackling the continuing de facto segregation in the NI education system".
NASUWT General Secretary Dr Patrick Roach said discrimination was damaging to children's education and to the wellbeing and careers of teachers.
"This legislation is compromising efforts to tackle prejudice and hatred and conflicts with the goal of social inclusion which schools should be working to nurture and promote," he said.
"No teacher should be denied opportunity to teach or to lead schools on the basis of their religious belief."
NASUWT National Official Northern Ireland Justin McCamphill said the exception was outdated and needed to be removed.
"We are calling on the administration to remove this and ensure that every teacher has equality of opportunity and is able to apply for work in any school regardless of their religion or perceived community background," he said.
"Removing the teacher exemption is necessary to tackle endemic nepotism and lack of diversity in the teaching profession."