Susan Ward - a primary depute headteacher - is honest about the impact that the national qualification for aspiring heads had on her initially: she wondered why on earth she had signed up for “this torture” and admits that she “freaked out”.

“Every stage of the process brought more ‘new’,” wrote Ward, who works at Kingsland Primary School in Peebles, in a recent blog. “New thinking, new ideas. New conversations about old practices that made what I’d always done suddenly look pretty shoddy. I freaked out. I felt stressed, anxious, panicky.”

But Ward, who was a principal teacher when she started the course, persevered and last month found out that she had passed.

She says that the master’s-level Into Headship course - which she undertook through the University of Edinburgh’s Moray House School of Education - has made her better at what she does now and far better prepared to be a headteacher.

Speaking to Tes Scotland, Ward, who has been teaching for 13 years, says: “[Becoming a headteacher] doesn’t terrify me as it once did and I feel I will be going in with my eyes open to the huge challenges inherent in the role. Knowing how hard it will be and still wanting to do it, I think, is empowering in itself.”

Ward is not alone in praising Into Headship, which was designed by the Scottish College for Educational Leadership with the profession and teacher education institutions. One teacher from Argyll and Bute, Julien McKenzie, describes the course on Twitter as the “gold standard” when it comes to education leadership courses.

Meanwhile, Stuart Clark, the head of Port Glasgow High School in Inverclyde, who completed the course in 2016, describes it as “very worthwhile” and says he is now a better headteacher as a result of “the additional study, critical reflection and professional debate and discussion”.

However, there are still concerns about whether there will be a large enough pool of candidates through the qualification by 2020, when Into Headship is due to become mandatory for all new state school headteachers.

The qualification was first delivered in 2015 and so far 397 teachers have completed it, with a further 168 due to undertake it this year.

Jim Thewliss, the general secretary of School Leaders Scotland, which respresents secondary headteachers, says that Into Headship is “definitely seen as worthwhile”. However, he adds that while there may be enough candidates by 2020 to fill vacant posts, the concern is whether there will be enough to give councils choice over who they appoint.

He says: “We have reservations over the number available to make up short leets and to provide enough diversity of experience to enable the selection of a candidate with the background and experience to enable them to deal with the specific circumstances of an individual school.”

Many teachers start the year-long course just because they need the qualification in order to advance, says Dr Joan Mowat, who is the Into Headship course leader at the University of Strathclyde. But they soon get “hooked” on the learning, she adds.

“A lot are anxious coming back into an academic environment, particularly if they haven’t studied for a long time,” Mowat explains. “By the time they come through the course, they have grown in confidence and that largely dissipates, and many are talking about how they are going to continue that learning beyond the course.”

She has been evaluating how satisfied students are with the course and the impact it is having, as well as what led to Scotland recognising that what it was doing was “no longer fit for purpose”. The student responses were “almost overwhelmingly positive”.

In an as yet unpublished paper entitled New Directions in Headship Education in Scotland, Mowat writes that one of the aspects that students valued the most about Into Headship was the opportunity to network with other aspiring headteachers from different local authorities. The University of Strathclyde course last year drew in teachers from five councils, 21 of whom were from primary and 12 from secondary.

One criticism made by “a significant number of students” was that they would have liked additional support in academic reading and writing, the paper states. One participant commented: “‘I would have appreciated 1:2, 1:1 tutorial seminars as I know I could do with more guidance on critical writing (I’m aware this would be a huge ask though).”

Mowat says that a revamped headship qualification became necessary due to “significant changes in our understanding of educational leadership and a move towards more democratic forms of leadership”.

So while its predecessor, the Scottish Qualification for Headship (SQH), was about managing schools, Into Headship is about creating leaders, says Mowat.

SQH included modules called “managing people” and “managing resources” and that content is still studied, but it is not the “end point”, she explains. Into Headship is also about teaching aspiring heads to be critical and to look beyond their school.

Mowat adds: “We want them to understand what it is to be a headteacher, the policy context and the ideas underpinning that. We give them extensive reading and, although they are initially anxious about that, the feedback is, ultimately, they really value it.”

The reading is not just about leadership because the teachers have to understand what it is they are trying to lead, so it can also be about topics like literacy and nurture, says Mowat. “If they are not informed, how can their staff be informed?” she asks.

Ward says Into Headship taught her that to be a good leader you have to take people with you; to slow down and listen more, and that “my way is not always the best or only way”.

In her blog, Ward concluded: “It has been hard and it has been scary. But it has also changed everything.”

Tes Scotland contacted the Scottish government to ask whether enough candidates were coming through the system to ensure high-quality competition for headteacher posts.

A spokesman says: “Headteacher recruitment is a matter for local authorities and it is for them to ensure they have enough teachers joining the Into Headship programme. The Scottish government continues to fund the course fees of all programme participants and we are pleased with the level of recruitment to date.” He added: “We are also committed to launching a headteacher recruitment campaign later this year and continue work with partners through the Headteacher Recruitment Working Group, which is jointly chaired between Scottish government and [local authorities body] Cosla.”

Tes Scotland also asked the government to clarify whether the Into Headship qualification would also become mandatory for all new independent school headteachers by 2020.

The spokesman says: “No, independent schools are not included within the scope of the draft regulations that we consulted on in early 2017.

“This followed representations from the independent sector, who argued that the role of school head in many independent schools was significantly different from that of local authority headteachers, making the qualification less relevant while potentially impacting negatively on their ability to recruit.”