Many headteachers would agree that the teacher shortage is the most pressing issue facing Scottish schools.

And without teachers in front of classes, there can be no progress on the Scottish government’s key pledge to narrow the attainment gap between advantaged and disadvantaged children, union leaders warn.

Yet professionals from overseas are struggling to secure visas to take up posts in Scottish schools that are crying out for staff (see the case studies of Haley Palmer and Amanda Choffe on page 8).

Now - as the recruitment crisis plaguing schools looks set to continue, or even worsen - the Scottish government has thrown its weight behind the campaign by our sister publication Tes to relax visa rules for teachers from overseas.

The #LetThemTeach campaign is calling for the whole teaching profession to be placed on the “shortage occupation list”, which gives higher priority for visas.

Currently, only teachers in four subjects - maths, physics, computer science and Mandarin - are on that list.

But, according to the SNP, the status quo is “not meeting Scotland’s needs”, which is having “a negative impact on our public services, our economy and our communities”.

The Scottish government says it has lobbied in the past for more secondary subjects to be added to the list - but to no avail.

In recent years, the Scottish government has introduced 11 new routes into teaching, increased the number of universities teachers can train in, and funded more places on teacher education courses, all in a bid to address the teacher shortage.

It says it appealed to the Migration Advisory Committee back in 2016 to include more secondary subjects on the shortage occupation list - including English, home economics and design and technology. But that plea was rejected, with the committee finding there was “not sufficient evidence to conclude that these teachers are in shortage”.

Now - like Tes - the Scottish government is pushing for all teaching jobs to be placed on the list so that teachers from overseas who are keen to work in Scotland can stay. “We support the Tes campaign on visas,” a Scottish government spokeswoman says. “The current migration system is not meeting Scotland’s needs and this is having a negative impact on our public services, our economy and our communities.

“There is a clear case for the Scottish government, accountable to the Scottish Parliament, to set the rules for a migration system tailored to Scotland’s needs. While teaching remains an attractive career in Scotland, we know there are challenges in rural areas and in some specific subjects. It is disappointing that the Migration Advisory Committee did not respond to our call for more secondary subjects to be added to the shortage occupation list.”

To qualify for tier 2 visas aimed at skilled workers from outside the European Union, applicants require a “certificate of sponsorship” from their prospective employer and generally need to have a job offer with a salary of at least £30,000.

But there is a cap on the number of tier 2 visas that can be handed out every month, and when this is hit, a points-based system comes into play, which is heavily weighted towards applicants’ salaries. In March, the salary threshold to qualify hit £60,000.

The starting salary for teachers in Scotland is £27,438; the most an unpromoted Scottish teacher can earn is £36,480.

If, however, a job is on the UK government’s shortage occupation list, it attracts more points, which means that applicants do not need such a big salary.

The leaders of Scotland’s key professional associations are also lending their support to the #LetThemTeach campaign - including the EIS teaching union, the Scottish Secondary Teachers’ Association and heads’ organisations School Leaders Scotland and the AHDS.

EIS general secretary Larry Flanagan says that the growing recruitment and retention problem facing Scottish schools is no longer confined to specific subjects or geographic areas but is nationwide.

Restrictive visa rules that deter qualified international teachers from working in Scotland “only add to the problem”, he says.

The restrictions and teacher shortages are felt particularly acutely in rural areas, says Greg Dempster, general secretary of the AHDS. In Scottish primaries, headteachers and deputes are covering classes and “stretching themselves extremely thinly” so children do not have to be sent home, he adds.

The shortages jeopardise the government’s flagship pledge to narrow the attainment gap, according to Jim Thewliss, general secretary of School Leaders Scotland.

“We talk about raising attainment but we’ll not make progress on that until we have got the right number of people in front of classes,” he says. A lack of teachers also means schools are having to narrow the curriculum, he adds. “We would support anything new that brings the right people into the profession.”

Thewliss points to severe recruitment difficulties, saying: “Headteachers are so often interviewing penny numbers of people and hoping in among those penny numbers there is going to be a person they want. This is about attracting people into the profession, keeping them and that whole notion of increasing the diversity of the profession.”

A Home Office spokeswoman says the UK government fully recognises “the vital contribution that international professionals make to the UK”. Decisions about immigration are based on evidence and the independent Migration Advisory Committee has been asked to review the shortage occupation list, she adds.

“The Migration Advisory Committee will look at which posts are in national shortage, and should therefore be given priority when allocating tier 2 places,” the spokeswoman says, adding that there are no current plans to introduce a devolved immigration system.

Tes has created a parliamentary petition to stop non-EU international teachers from being turned away from Britain.

If the petition hits 10,000 signatures, the government is obliged to formally respond to it. If it hits 100,000 signatures, it will be considered for a debate in Parliament.