Hundreds of teachers have defected from the EIS to join other teaching unions in protest over the recent national agreement, it was claimed last week.
And a movement has sprung up aiming to create a brand new union for primary teachers.
Delegates at the Scottish Secondary Teachers' Association and NASUWT annual conferences claimed they were beginning to match, if not surpass, the number of EIS members in many schools.
SSTA general secretary Ann Ballinger told TESS that 200 people had joined in recent weeks after cancelling their EIS payments, citing disillusionment over its stance on pay and conditions; membership was said to have reached "about 9,000".
Her union had even taken a number of calls from primary teachers asking if they could join, she added, although the SSTA has no immediate plans to dilute its secondary-only status and take members from the primary sector.
Maggie Nesbitt, SSTA representative at Clackmannanshire's Alva Academy, said that membership in her school had risen from 20 to 38; like other delegates, she told TESS that this had happened without any attempt to poach EIS members.
"I've had teachers who've been EIS members for 20 years asking for forms because they're frustrated and don't feel they're being adequately represented," she said. "It's the first significant change in our membership in the 11 years I've been at the school."
Central area representative Ian Maclean, who covers Clackmannanshire, Falkirk and Stirling, confirmed that a number of EIS members said they were considering a switch; 11 had already done so in one school. Gordon West, Aberdeenshire assistant district secretary, knew two people in his school who had cancelled direct debits to the EIS in the previous week. An SSTA representative at an east of Scotland school said eight former EIS members had joined in recent weeks.
A number of SSTA delegates suggested that many EIS members were waiting until its annual general meeting next month before deciding whether to jump ship.
NASUWT Scotland organiser Jane Peckham said that since the end of April, a significant number of EIS members had switched to her union, although she was unable to provide figures.
EIS general secretary Ronnie Smith, who argued that his union had supported a deal that could not be improved in the current climate, said: "As always in times of unrest there is an increased level of membership movement among teacher unions. This has seen an increase in both members leaving and applying to join the EIS."
He insisted that teachers' interests would be much more effectively represented through a single, united organisation, adding: "While some smaller unions may, in the short term, benefit from poaching members from other organisations, ultimately those who are poached will be disappointed and the capacity of teachers collectively to resist cuts will be diminished."
A Facebook page, meanwhile, has revealed the potential emergence of a new union, with the working name of the Scottish Primary Teachers Association.
The page links to the Facebook page for the "Reclaim EIS" movement, set up in protest against the union's stance on the pay and conditions talks. It includes a 9 May welcome message describing the online presence as "the first step to creating a body to represent primary, nursery and special education professionals". A more recent message invites four or five volunteers to form a committee of management.
The SSTA has no involvement with the SPTA, said its general secretary, Mrs Ballinger, although she would be "happy to talk" to the mooted new body.
SSTA members gave unanimous backing to a motion promoting the use of industrial action to protect their conditions of service, although Mrs Ballinger said it was more likely to take the form of a "work to contract" than strike action.
Outgoing president Peter Wright said teachers were "being thrown to the wolves". The debate became particularly heated on the subject of short- term supply teachers, whose pay could drop by up to 46 per cent.
`Divisive and unsound'
Anger over the recent teachers' agreement on pay and conditions dominated debate at the SSTA annual congress, but delegates also became fired up over other issues.
There was "total opposition" to the absence of external assessment in the National 4 qualification, as set out in a motion describing current plans as "divisive and educationally unsound".
Renfrew area representative Val Liddell, who proposed the motion, said external assessment was "really important" to parents and employers, and that the lack of it would make a qualification "not worth the paper it's printed on".
Faculty structures, described in a motion by Ayrshire's Euan Duncan as "no more than a cost-cutting exercise detrimental to the provision of high- quality education", were also unanimously condemned.
A number of delegates stressed that they had extremely capable heads of faculty - but even they could not cope with the demands of overseeing several subjects.
East Dunbartonshire delegate Keith Gilmour called for action against classroom indiscipline. He linked behaviour issues to an inquiry under freedom of information legislation earlier this year, which showed that 1,400 teachers in Scotland were off work with stress.