More agency supply teachers who work regularly in the same school will be entitled to the same rates of pay as permanent employees, after ministers made an important concession in new employment laws.
New rules formulated last year said that agency workers would qualify for equal pay rates if they worked at least one day a week in the same school for 12 consecutive weeks.
Teaching unions had argued that supply teachers would suffer unduly because long and regular school holidays would inevitably interrupt their qualification period.
However, ministers at the Department for Business, Innovation and Skills have now confirmed that the periods when businesses or schools are closed should not count as interruptions to service.
The move has been welcomed by unions which argued that supply teachers, who are often paid less pro rata than those in permanent positions, would have been unfairly penalised.
However, they believe that the legislation still does not go far enough.
Martin Freedman, head of pay, conditions and pensions at the Association of Teachers and Lecturers, said supply teachers who hop between jobs in different schools within the same authority should also qualify for equal pay, even without 12 weeks' service.
He added that all teachers should also have equal rights to pensions, holidays and sick pay.
He said: "We are glad there has been a U-turn on the issue of the 12-week qualifying period because teachers would suffer far more than any other workers.
"It seems that the ministers have seen sense. However, a lot more needs to be done to give supply teachers parity with permanently employed staff."
Currently, agency teachers generally only accrue the statutory 28 days' holiday and statutory sick pay and have no right to join the Teachers' Pension Scheme.
Despite the disappointment of unions that the new laws do not embrace all aspects of pay and conditions, recruitment agents are now preparing for a potential bureaucratic nightmare when the laws come into effect in October 2011.