Some schools 'unable to find staff they need'
Some Scottish schools have had to advertise multiple times in order to fill teaching posts, according to figures obtained by the Scottish Liberal Democrats.
Freedom of information requests submitted to all of Scotland's 32 local authorities found one post had been advertised as many as 14 times.
The responses also showed some open posts had had no applications.
Scottish ministers said teacher numbers were at their highest since 2010.
The Lib Dems said they had received responses from 26 councils, with one secondary post - for a technical education teacher in Aberdeenshire - being advertised 14 times. It attracted a total of four applications.
In the same local authority area, primary teacher vacancies in Banff were advertised seven and nine times, according to the Lib Dems.
On the other side of the country, a vacant primary school teaching post in East Ayrshire was advertised nine times.
Meanwhile, the figures showed a teaching post in Dundee had been vacant since June 2017, and a post to teach Gaelic in Aberdeen was advertised seven times - with one application received.
Analysis by Jamie McIvor, BBC Scotland education correspondent
There's been concern for many years about the difficulties experienced filling some vacancies in remote and rural areas.
Often qualified applicants need to be persuaded to move to the area - and the problems recruiting teachers are often similar to those filling other skilled and specialist jobs.
Relatively high house prices in some areas have also led to difficulties - teachers' pay is standard across Scotland.
More people are going into teacher training - but not all the extra places created in teacher training are being filled.
Some councils have also noted problems filling vacancies in specific subject areas, including the STEM subjects and home economics.
The teachers unions are currently campaigning for a 10% pay rise, which they claim would help restore the value of salaries.
They argue this would also help encourage more graduates to become teachers and help retain people within the profession.
Responding to the Lib Dem figures, Aberdeenshire Council said some specialisms could be "particularly challenging to fill".
It added: "With a large education estate, the recruitment of teachers is an ongoing task for the council and we have used a number of innovative measures in recent years to attract people to Aberdeenshire."
Scottish Lib Dem education spokesman Tavish Scott said it was "extremely troubling" that teaching posts were being repeatedly advertised.
He said: "These new figures demonstrate the pressure in schools for teachers across all subjects.
"Head teachers are simply unable to find the staff that they need.
"The data published by Liberal Democrats today reveal that it is now all too common for councils to advertise jobs and not receive a single reply.
"This applies to core subjects such as maths and English. This will have a huge impact on Scottish school pupils' learning."
Last month, the Scottish government said the number of people in teacher training in Scotland had gone up for the third year running.
It also reported that the number of vacancies being advertised for more than three months had fallen sharply.
In a statement this weekend, the Scottish government said teacher numbers were currently the highest since 2010, with primary teachers at the highest level since 1980.
Education Secretary John Swinney said: "We want to keep people in the profession and to attract new entrants into teaching.
"That's why we have increased targets for recruitment into initial teacher education, created new routes to make it more practical and flexible for people to access courses and run a teacher recruitment marketing campaign.
"There are also fewer teaching vacancies across the country, including significant reductions in jobs advertised for more than three months, demonstrating the impact of our investment in attracting new talent to the profession."