New rules designed to curb headteacher pay could lead to a “two-tier system” with the wages of academy heads rocketing while the rest face a cap, the profession’s leaders have warned.

Under the plans, revealed earlier this week by the School Teachers’ Review Body (STRB), heads in maintained schools will be barred from earning any more than pound;140,000 - a ruling that will not count in academies.

The rules, accepted this week by education secretary Michael Gove, mean that heads will only be able to earn 25 per cent extra on top of their basic salary for taking on additional responsibilities such as executive headship or consultancy.

At present, governors in the largest and most challenging schools can offer heads whatever it takes to recruit them. Although records show a handful of heads are now earning pound;180,000, the new rules will not be applied retrospectively.

However, the new pay cap is accompanied by a “get-out clause” which allows governors to exceed the 25 per cent extra limit in “wholly exceptional circumstances”.

Those who want to award more will be subject to much closer scrutiny in their decision-making. A business case will have to be presented to the full governing body, and “external independent advice” must be sought in reaching a decision.

Although it can be difficult to obtain detailed information on heads’ pay, it is generally accepted that academy leaders have secured some of the most generous deals.

Heads have warned that a two-tier situation could develop if extra pay is limited in maintained schools but not in the growing number of academies. The Department for Education (DfE) this week announced that a third of all secondary schools are academies or in the process of becoming one.

Latest official figures indicate that about 200 teachers in the leadership group now earn more than pound;110,000.

Brian Lightman, general secretary of the Association of School and College Leaders, said: “We believe this system (the STRB recommendation) is transparent, but it doesn’t make sense if it only applies in some schools. If they are attempting to produce a format for headteacher pay, it should apply to all schools.”

Russell Hobby, general secretary of heads’ union the NAHT, agreed. “If these recommendations are not applied to a growing number of (academies), the proposals will have an extremely limited impact,” he said.

Emma Knights, chief executive of the National Governors’ Association, said governors would welcome more clarity on pay for senior leaders, but not applying the rules to academies risked a “two-tier system”.

The DfE has said there are no plans to introduce the limit in academies because they are “accountable to parents and taxpayers through their funding agreements”.

Both heads’ leaders also complained that the impact of the proposals would be limited because they fail to address how to calculate remuneration for executive headship and work with other schools.

Consultation on the proposals ends on 3 June and the measures will be introduced to new contracts from September.

PAY REPORT: Out in the open

A report by the School Teachers’ Review Body has said full public disclosure of heads’ salaries is “a desirable longer-term aim”.

But it added that publication of salaries was “not a sufficient response” to the need to establish limits on heads’ pay.

“Our recommendations should encourage more structured and sustainable decision-making on headteacher pay which both individuals and governing bodies will, over time, be increasingly content to justify to a wider public audience,” the report said.

Original headline: Deal to halt heads’ runaway pay risks two-speed system