Elizabeth Maginnis, leader of the management side of the Scottish Joint Negotiating Committee, told primary heads at their conference last week that she favoured an overhaul of pay and conditions.
But Mrs Maginnis warned: "Until the penny drops with the Educational Institute of Scotland our hands are completely tied."
It was "bloody ludicrous that Scottish education is lumbered with conditions of service appropriate to 20 years ago". A transfer of resources to the primary sector could be achieved through some redistribution from secondary and some new money.
Members of the 1,400-strong Association of Head Teachers in Scotland, however, raised the stakes by agreeing unanimously to press ahead with a test case under equal pay and sexual discrimination legislation, although this could take several years.
The association has been encouraged by several equal pay verdicts against the former Strathclyde Region.
Euan Mackie, head of Lochardil primary, Inverness, told the association's conference in Dunblane that the argument was principally about pay, although conditions in secondaries were far superior because of their extended promoted post structure. The difference in levels of pay between a primary head and secondary head in charge of schools of comparable size could be as much as Pounds 7,000.
Mr Mackie said: "The difference in secondary salary and management structures is a legacy of the past which has provided a generous career structure for male-dominated secondary headteachers and places them at the top of a complex web of promoted posts.
He added: "Nearly all secondary headteachers are men while primary headteachers are predominantly women. Because of this disproportionate balance and the corresponding disparities in resources and salary, equal opportunity legislation has a relevance to our case through the Equal Pay Act and sex discrimination laws.
"This places responsibility on employers to be aware that current agreements, including the SJNC, may be discriminatory and open to legal challenge."
Speaking with the support of the AHTS executive, Mr Mackie claimed that primary heads were expected to deliver many of the same initiatives as secondary heads but with far fewer resources.