The future of Catholic education in Northern Ireland is under "significant threat" from planned reforms, Cardinal Sean Brady has claimed.
He said plans to centralise control of education could "undermine the ethos" of Catholic schools.
Education minister Caitríona Ruane has said the changes are necessary to create a more effective system.
The cardinal will appear before the assembly's education committee on Wednesday to express his concerns.
His main focus is on the new Education and Skills Authority.
It will take over the main duties of the Council for Catholic Maintained Schools (CCMS), including the employment of teachers, reducing the CCMS to an advisory role.
The cardinal, who is the head of the Catholic Church in Ireland, appealed to people to lobby politicians to "safeguard the right of parents to have their children educated in Catholic schools".
He asked politicians to "respect the hard-won right of Catholic parents to have fair and appropriate support from the state for Catholic schools".
The cardinal was speaking at a mass celebrating the opening of St Patrick's College in Dungannon, County Tyrone.