An industrial tribunal in Glasgow this week dismissed a claim from principals of outdoor education centres to be paid the same as headteachers of residential centres.

This is the third equal pay battle won by Strathclyde and its 12 successor authorities, following victories in the past two weeks in cases involving acting principal teachers and pre-five heads.

In a 36-page written judgment, the tribunal ruled that three male principals, on local government conditions of service, were not in the “same employment” as three women headteachers employed under conditions set by the Scottish Joint Negotiating Committee.

Nevertheless, the tribunal found the principals were “in the same service” as heads and that for practical purposes there was no difference in the work they did.

But there appeared to be no sex discrimination behind substantial differences in pay between headteachers and principals, according to the tribunal.

Ian McPherson, the solicitor acting for the councils, welcomed the judgment but added: “The way to resolve these matters is not through the legal process but through negotiations. This case has taken time, effort and 17 days’ evidence. We have been waiting on the decision since December 4 last year. ”

The verdict could also affect a similar case brought by assistant principals of outdoor centres. A ruling is not expected until later this year. Together with the principals, 26 staff are involved.

Linda Marsh, former assistant director of education in Strathclyde, who is masterminding the councils’ defence in a string of cases, said: “The decision focused on cross-collective bargaining comparisons and closed the door on staff comparing themselves with teachers on SJNC conditions.”

However, Susan Blease, a spokeswoman for Harper MacLeod, the firm of solicitors acting for the outdoor principals, said she was “somewhat surprised at the decision” and was assessing the prospects for an appeal.

The tribunal noted historical differences between residential and outdoor centres. Residential centres were staffed by teachers and outdoor centres by instructors, although both had come together in the 1990s, a fact acknowledged by Strathclyde officials.

Residential centres were established 30-40 years ago to provide a country experience for city children, while outdoor centres, a more recent development, provided a residential experience through outdoor pursuits, the tribunal reports.

Since the tribunal took evidence, both types of centre have been under threat of closure following local government reorganisation and cuts in education budgets.

Meanwhile, the Scottish Secondary Teachers’ Association is taking legal advice about an appeal to the House of Lords over the decision of the Court of Session to throw out its equal pay case. The union could face costs of more than Pounds 100,000 if it continues. A decision will be taken next week.

Ten women members claimed the pay of principal teachers while carrying out their duties and were initially supported by an industrial tribunal and the Employment Appeal Tribunal.