TOO many pupils are staying on at school until sixth year putting further pressure on Scotland's scarcity of teachers, according to an expert.

The claim comes as Scotland struggles to recruit enough teachers, with particular shortages in key subjects such as science and maths.

Research by the Herald this summer showed there were more than 700 unfilled teacher vacancies before the start of term, with the shortfall blamed on a rise in numbers quitting the profession early and historic under-recruitment.

In the past twenty years the proportion of pupils staying on at school has increased dramatically from 42 per cent in 1996 to 62 per cent in 2016.

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Douglas Weir, emeritus professor of education at Strathclyde University, said staying on was not always the best option for pupils - and was also a drain on teaching resources.

Writing in the Herald he said: "Why do over 60 per cent of an age group stay in school right through to sixth year?

"Almost half of them will not go immediately to university and might be better taking an earlier step towards independence through experience in college, training or work.

"If there are many staying in school to fifth and sixth year through a form of inertia, we need to act on this, and staff the senior school accordingly."

Mr Weir, a former dean of the faculty of education at Strathclyde University, also questioned the Scottish Government's current approach to recruiting teachers.

Ministers have opted for new fast-track teacher training courses as well as financial incentives for some subjects.

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Mr Weir believes a better approach would be to re-consider the qualifications and expertise required of a secondary teacher.

He said: "If we use a concept of the generalist degree to help determine the size and type of the teacher workforce, we can envisage more of the teacher workforce being trained to teach two or three subjects.

"If they were teaching all of their subjects regularly, even if only in the first three years of secondary, they would be perfectly competent.

"If a broad general education in these years is a national priority, then we need to develop a teacher workforce specialising in that phase ... helping to ensure that teachers in shortage subjects can be better deployed."

Eileen Prior, executive director of the Scottish Parent Teacher Council, agreed that pupils sometimes stayed on for the wrong reasons - including attending end of sixth year celebrations.

She said: "We have to work harder to ensure the range of options is discussed and attractive, and celebrating fourth and fifth year leavers more than at present would be a good start.

"Sixth year is an important opportunity to mature, to make learning choices and to try new activities such as fundraising and volunteering, but college, apprenticeships or work are great opportunities to develop skills and help pupils move into adulthood."

Larry Flanagan, general secretary of the Educational Institute of Scotland teaching union, said there was merit in pupils staying on at school.

"It’s probably the case that the majority of students in S6 are upgrading or achieving National 5 and Higher qualifications so the year is critical for them," he said.

"Advanced Higher is a sound qualification for students who are clear about their university choices and sixth year also allows some breadth of experience in which may have been squeezed out in fifth year."

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The General Teaching Council for Scotland said it was already considering a registration for teaching staff that would span primary schools and the first three years of secondary.

Ken Muir, chief executive of the GTCS, said: "We have been developing a range of flexible approaches to registration and are currently planning the specific requirements of a category of broad general education which would cover the age range of three to 15-years-old.

“There is the potential for several benefits to registrants, schools and children from this development and we are already aware of individuals who would like to take up the opportunity of working across the sectors."