You don’t need to have passed Advanced Higher Maths to understand the complaints from the Educational Institute of Scotland (EIS) about teachers’ pay.

With inflation having regularly outstripped pay rises for more than a decade, teachers are effectively getting less now for the job than they were in 2003.

According to figures from the leading teaching union, the gap between pay levels 13 years ago and those of today is eight per cent if inflation is measured using the consumer price index, and double that if you use the retail price index.

Either way, the recent agreement on a two per cent pay rise for 2017/18 was welcomed by teachers after negotiations with councils and the Scottish Government turned into an endurance test. But it was only ever seen by most as a first step. Today, the EIS will post warning that a similar deal for 2018/19 will not be acceptable, as the parties prepare to reseat themselves at the negotiating table.

That is problematic for the government – while finance minister Derek Mackay lifted the public sector pay cap in his recent budget, he promised only a two per cent increase for those, such as teachers, on above £30,000 a year. Such a rise would do nothing to meet the EIS’ aspirations for a rise which begins to return teachers’ pay to “pre-austerity levels”.

The other issue for the Scottish Negotiating Committee for Teachers (SNCT), which acts on behalf of councils and ministers, is the recent deal secured by college staff. This sees unpromoted lecturers on basic starting salaries of £40,000. Unpromoted teachers, in contrast, start on around £36,000.

Many teachers will feel that deal has set a precedent in terms of the value attached to their vocation. But bringing starting salaries for unpromoted teachers to the same level as in colleges would require a pay increase of more than 11 per cent.

That college deal was only achieved after strike action, so it is perhaps little surprise the EIS is now threatening similar action in schools. As the institute represents more than 80 per cent of Scotland’s teachers, this is more than mere sabre-rattling.

Strike action is in nobody’s interests, least of all that of pupils. But teaching is a vital job, as recognised by the priority the Scottish Government has placed on education. It is a hard job, made harder by increasing expectations and regular demands for change. It is difficult to dispute that staff have been asked to do more while pay levels have been allowed to stagnate. Restructuring has limited opportunities for promotion.

This in itself is demanding of some sympathy, but there is wider evidence to support the claims being made by teachers.

Salaries in Scotland have fallen behind those for teachers in other OECD countries, even those with financial problems of their own. Meanwhile many councils face a recruitment crisis – with schools starting this academic year with more than 700 posts unfilled, and hundreds more jobs having to be re-advertised. There is pressure to ensure teaching continues to be an attractive career, not just to make sure existing teachers are satisfied enough to stay put.

The importance of reaching a fairer settlement on pay is not just that of rewarding existing teachers for the job they do. There is also the need to encourage more young people to take up teaching, and to persuade older workers in other professions – particularly those from a science, engineering or technological background – to consider a career change.

All parties should seek an early settlement and a fair one. The EIS aim of returning pay to pre-austerity levels may be ambitious for a single pay round. But whatever way you calculate it, Scotland’s teachers deserve more than appears so far to be on the table.