The teaching profession is becoming increasingly casualised, our largest teaching union has claimed.
The NASUWT - meeting for its annual conference today in Belfast - said the system of substitute teachers was being exploited. A central register, the Substitute Teachers' Register (STR), enables schools to identify qualified teachers who are available for part-time work.
The union said these teachers were valuable to cover short-term absence. However, it said there was evidence of "growing exploitation of the system".
The NASUWT will debate a motion today calling for an end to the practice.
General secretary Chris Keates said it should be outlawed.
"Substitute teachers are a vital resource and they should be valued but all too often they are subject to exploitation," he said.
"Paying teachers on a daily rate for long-term cover simply to keep down costs by denying teachers entitlements to decent terms and conditions including holiday and sick pay is a practice which should be outlawed."