Primary headteachers who are demanding to be put on the same pay scale as + secondary heads are to launch a formal grievance against a local authority + within six weeks.The complaint could end in an industrial tribunal and a + renewed attempt by a union to use equal pay legislation to address teacher + grievances. Should the Scots heads win, it could cost millions of pounds in + higher salaries and lead to knock-on claims throughout Britain.The Association + of Head Teachers in Scotland has confirmed plans to launch a test case, despite+ last week's equal pay defeat in the Lords for the Scottish Secondary Teachers'+ Association (page four).The SSTA failed to convince the Law Lords there was + any sex discrimination involved in the former Strathclyde Region's decision not+ to pay nine women teachers the salary of a principal teacher. The women had + taken on added duties in new departments, such as computing, but were never + paid extra.But Jim Smith, the AHTS's secretary, said the verdict would have + little impact on the heads' case, which has been in the pipeline for more than + a year. "The SSTA defeat should not affect us. Ours is a different case and we+ are making it on different lines," Mr Smith said. He believes precedent is in + the association's favour. "Primary class teachers are paid on the same scale as+ secondary teachers. The contract and hours of work are the same. That should + simply be extended to headteachers. There are one or two avenues we can take + and we are working on that."The association is likely to argue for pay parity + on grounds of equal value, rather than the like work argument that the SSTA + relied on. It wants all heads of primaries and secondaries to be placed on the + same scale and for the school roll to be the sole criterion for pay + levels.Primary heads that mount a test challenge will use neighbouring + secondaries as a comparison. The Equal Opportunities Commission is lending + support but, so far, no financial backing after heavily supporting the SSTA. + The costs in that case ran to well over #163;100,000.Mr Smith said: "It would + still mean secondary heads would be paid more because they have got bigger + schools. But it could mean most primary heads would get an increase and in some+ cases it would be substantial. You are talking about several million pounds + more and that could be the trouble for the Government."The association believes+ the Scottish Joint Negotiating Committee could have rectified the differential+ but failed to act.Primary heads are almost certain to claim sex + discrimination, the key test under equal pay legislation, as the Lords + identified. More than 90 per cent of primary staff are women but a little over + 70 per cent are heads. Men are therefore disproportionately represented.