Teaching unions and political opponents made the plea yesterday after a survey by Scottish Labour found 84% of local authorities did not fill all requests for short-term cover in 2011/12.
In addition, some 52% of councils also experienced problems filling long-term supply requests over the past year.
The highest rate of non-fulfillment for long-term supply was in Edinburgh, while for short-term supply the greatest problems were in West Lothian.
Of the local authorities in Scotland holding accurate records, half revealed a reduction in the number of teachers held on their supply lists.
The biggest drop in the number of supply teachers available was in Aberdeenshire, which lost 275 teachers from the supply list in one year alone.
The poll, which featured responses from two-thirds of councils, follows a controversial deal between council body Cosla, the Scottish Government and teaching unions.
Councils were asked to fund Government priorities, such as providing jobs for newly qualified teachers and maintaining pupil-teacher ratios in P1 to P3.
In return, Cosla drew up changes to terms and conditions to save about £60 million, including lower salaries for supply staff.
It means supply staff must work at the lowest daily rate of £78 for five consecutive days in the same school before their pay rises to the normal rate of £145.
Hugh Henry, Scottish Labour's education spokesman, said: "It is clear this penny-pinching deal from the SNP is having a devastating impact on the education of Scotland's young people. The current situation is unfair, unacceptable and unsustainable.
"Teachers are being offered stints of five days or less so employers can avoid paying them a higher rate. It is little wonder so many local authorities are struggling to fill requests for supply.
"This cannot go on. It is not fair to pupils who are facing a succession of different faces, and it's not fair to teachers who worked hard for their qualification and deserve a fair day's pay for a fair day's work."
Ann Ballinger, general secretary of the Scottish Secondary Teachers' Association, said: "We have made it clear from the start it is irresponsible to expect fully qualified teachers to be paid £78 for a day's work when their normal rate is £145.
"There are very few, if any, permanent teaching posts, so existing on a day of supply work is frequently the best teachers can get.
"This agreement was absolutely unfair on supply staff and, once again, we call on this cut to be removed."
Eileen Prior, executive director of the Scottish Parent Teacher Council, said: "The concerns we are hearing, primarily in the senior schools, is where pupils are heading towards qualifications and are finding classes not covered by specialist teachers.
"It can also be the case that classes are being covered by a succession of different replacement teachers which breaks the continuity of lessons at this important time."
A Government spokesman said one of the reasons supply staff were in shorter supply was because many were finding full-time permanent jobs.
He said: "These figures do not take into account the high numbers of fully qualified teachers and probationers in employment, in line with this Government's commitment to providing a stable workforce. We want to achieve a strong, confident and reflective professional teaching workforce.
"That's why the Education Secretary announced a series of actions last week in response to recommendations made through the McCormac review of teaching employment."
He added: "The Education Secretary has also recently engaged in discussions with the teaching unions and local government on the issue of supply teachers and reached an agreement all three parties agreed was necessary. The Scottish Negotiating Committee for Teachers will continue to monitor the situation and we will take any appropriate action that is required."