The "deliberate targeting" of supply teachers' working conditions was laid bare at the annual conference of the Scottish Secondary Teachers' Association.
"The treatment of supply teachers isn't shabby - it's disgusting," said general secretary Ann Ballinger, as delegates told of colleagues earning little more than pound;50 a day - "Tesco rates", as some dubbed it.
Last year's national agreement on pay and conditions had been "cynical", said Mrs Ballinger, but "we had no idea how bad it would be".
She cited authorities who counted, and only paid for, the minutes a supply teacher stood in class; demanded a supply teacher arrive 30-60 minutes before the start of a paid contract; and treated cover for individual teachers as separate contracts, to avoid paying the higher supply rate.
The union had begun taking legal action on behalf of supply teachers; on each occasion the employer had come to a financial settlement, Mrs Ballinger said.
Members called on the Scottish Negotiating Committee for Teachers to hold a "thorough review" of supply teachers' contracts to ensure teachers receive proper remuneration.
Curriculum for Excellence was Mrs Ballinger's other big issue, with an increasing number of members reporting severe stress and "workloads which simply cannot be sustained".
She described Education Scotland's "deep audit" of schools' readiness for the senior phase of CfE as "ridiculously shallow", since it was compiled largely by local authority education officials rather than teachers.
Mrs Ballinger criticised the system of compulsory transfers emerging in Aberdeen, which has moved away from the traditional "last in, first out" approach. The SSTA opposes using attendance and discipline records instead, and she promised to challenge transfers made on this basis.
Past president Peter Wright called on other trade unions to join the SSTA in its "indefinite work to rule". Members said they were willing to work with other unions to protect working conditions, despite the divisions over last year's national agreement.
The union voted unanimously to "deplore" the abolition of the chartered teacher programme, and to demand assurances from the Scottish government that existing chartered teachers' rights be protected.
Proposer Anne O'Kane, from Fife, underlined the commitment made to the scheme by participants, not all of whom achieved chartered status; she compared this with the Scottish Qualification for Headship, which, she understood, no one had ever failed.
The union took a stance against local authorities that restricted use of social networking websites. Members backed a motion from Fife's Robert Macmillan demanding that all teachers have access to such online tools.
Proposer Rob Hands, Perth and Kinross, was "excited" by the new National 4 and 5 courses, but felt they were still a work in progress and national writing teams were needed.
One of the most enthusiastically received motions came from Joe Wallace, Aberdeen, who called on members to "take control of their own workload".
Fellow Aberdeen member John Gray received vigorous applause when he listed the "weasel words" of which teachers should beware, including: "It would be good for your career development."
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Early intervention measures supported
Guest speaker Dame Elish Angiolini threw her support behind early intervention measures. Taking money from the criminal justice system and putting it into the early years would solve the problem of the rising prison population, she said.
The former Lord Advocate told delegates how she had struggled at school with reading and writing, and needed additional support.
People did not remember what teachers did, but they never forgot how teachers made them feel, she added.