SCOTTISH Education Secretary Mike Russell recently described his controversial teachers' pay agreement with local authorities and the main teaching union as "not the best deal for everybody".

Surely that was an understatement. Under its terms, there were safeguards for newly-qualified teachers and an allowance for smaller class sizes but the quid pro quo was the imposition of the lowest hourly rate paid to supply teachers working for less than five consecutive days in the same school. The effect on many staff who fill in for illness or absence was to nearly halve their pay. In The Herald today, one of them complains they are treated like casual day labourers in the Third World. Now they have had enough.

All schools are sometimes dependent on supply teachers during pressure points, such as flu outbreaks or when permanent staff are undergoing training. Teachers are human. They fall ill and suffer bereavements, just like the rest of us. So the quality and commitment of supply teachers, and the day to day continuity they offer, can have an enormous impact on the prospects of children and young people.

Supply teachers are outraged with the EIS, local authorities and the Scottish Government and are now threatening to withhold their services for a week in the hope of forcing a rethink. They are justified in feeling they have been singled out for harsh treatment.

Under the new system, there is nothing to stop cash-strapped local authorities from employing a supply teacher for four days, then bringing in someone else for the fifth day, so as to avoid triggering a higher payment. They can even move the same supply teachers between different schools, as the "continuous" clause only applies to individual schools.

Unsurprisingly, there is now a shortage of supply teachers, especially outwith the Central Belt and in certain subjects because many experienced teachers are not prepared to work for less. As a result classes have to double up and there are even reports of pupils left in the care of unqualified staff. Anecdotal evidence suggests some teachers are leaving the profession or considering a downgrade to teaching assistant posts in their search for regular work. Others are taking posts in England or abroad.

The education of pupils faced with a succession of different supply teachers is bound to suffer. Parents of such pupils would be right to complain. The system is also unfair on supply teachers, some of whom were attracted into teaching from other professions by assurances that it offered a rewarding and stable career but who failed to land a permanent post after their probationary year. Retired senior teachers, who once upon a time were happy to fill in for a day or two a week, no longer find it worth their while.

This was a bad deal that affected those teachers least able to fight back. Councils are legally obliged to balance their books, while coping with pressure from the Scottish Government to reduce class sizes in lower primary, as well as maintaining the moratorium on the closure of rural schools. In a period of austerity, perhaps it is time for the minister to reconsider before the supply teacher shortage morphs into a crisis. Teachers like to tell their pupils that hard work brings rewards. Perhaps they might add, "unless you become a supply teacher".