The EIS union may have sealed the deal on the teachers' revised agreement, albeit with a small majority, but councils are facing the prospect of a legal challenge next session when some of the most contentious changes are implemented.
The Scottish Secondary Teachers' Association plans to use two pieces of legislation to challenge the cut in pay rate for the first five days supply teachers are employed - the Part-Time Workers (Prevention of Less Favourable Treatment) Regulations 2000 and the Fixed-Term Employees (Prevention of Less Favourable Treatment) Regulations 2002.
The general secretary of the UK-wide NASUWT union, Chris Keates, is also seeking advice over whether the deal would have an adverse impact on women and could therefore be challenged under discrimination legislation.
Ann Ballinger, SSTA general secretary, told TESS: "If one of these employees (supply teachers) is treated less favourably and materially differently from permanent employees, then that is illegal and we could take that to an industrial tribunal."
She said her union was also investigating whether it could mount a separate legal challenge on behalf of someone who had accepted lifetime conservation instead of redundancy when his or her job disappeared (following restructuring under the 2001 teachers' agreement) and was now losing lifetime conservation under the latest agreement.
The EIS, meanwhile, has come under fire from a section of its membership which campaigned against the deal. Rebadging itself as "Reclaim EIS", the "Reject EIS" movement's website is now debating its next move. One member, Brenda McCole, is urging those who voted against the revised deal to "jump ship and move en masse to the SSTA".
But another, John Dennis, argues that if large numbers of "No" voters leave the union, it is more likely that the leadership will "go for appeasement again and agree to still more erosion of our conditions" under the McCormac review of teachers' employment.
EIS general secretary Ronnie Smith acknowledged that the union's annual congress in June was facing stronger strike pressure than in recent years.
The ballot result at the end of April - 56.2 per cent voting to accept, 43.8 per cent to reject, out of a 42.8 per cent turnout - reflected the difficulty facing members, he said. "The whole negotiation was about limiting the damage that was being done, rather than an advancement of conditions."
The conditions of service working group of the Scottish Negotiating Committee for Teachers will this month embark on a substantial rewriting of the SNCT handbook to reflect the changes agreed under the revised deal, said EIS assistant secretary Drew Morrice.
The freeze on entry to and progression through the chartered teacher programme takes immediate effect, but changes to the deployment of supply teachers are not due to take place until August.
Original headline: Unions set to challenge new conditions