As its Torquay annual conference closed, the union called for reforms to give supply teachers better protection and for agencies to pay contributions towards their pensions.
The move follows demands for a fair deal for undergraduate teacher trainees, and better protection and support for newly-qualified teachers and assistants. Support for the latter reflects the ATL's inclusive"big-tent" philosophy. The union has already admitted classroom assistants and joined forces with the Association of University Teachers - but has kept its bar on heads being members.
The cost of supply cover has soared due to the teacher shortage. But the benefits are often not passed on to agency staff, said ATL deputy general secretary Gwen Evans.
The ATL will campaign for undergraduate trainees to get the same gants as postgraduates. Undergraduates at the conference said that up to half of students on their courses had dropped out for financial reasons.
David Guiterman, Cornwall executive member, said most newly-qualified staff at a recent training seminar in his county had been on temporary contracts. The ATL fears many newly-qualified supply staff will miss out on taking their induction, as the four-term deadline for completing it looms.
ATL delegates also raised concerns about stress on A-level students following the introduction of AS-levels. The union is to carry out an investigation into the issue.
Veronica Rodriguez of Mangotsfield school, Bristol, said this year's AS-level students had been guinea-pigs for the key stage two and three tests and GCSE reforms as well as Curriculum 2000. One student had told her that the exams had taken his life away and that he was so stressed he could no longer play sport or music.