Figures released under Freedom of Information laws have shown big variations in  how common “multi-course teaching” is around Scotland.

Investigative news platform The Ferret found, for example, that two of the most affluent and high-attaining parts of Scotland make little use of the practice, which can see pupils studying the same subjects at different levels - such as National 4, National 5 and Higher - working in the same class.

In East Renfrewshire, for example, five of the seven secondary schools offer all subjects as single-level classes. In the two schools that do make use of multi-level teaching, fewer than half of classes are delivered this way.

Survey: Teachers feel ‘blackmailed’ into multi-course classes

Background: Multi-course classes ‘norm in most Scottish schools’

Related: School delivers four maths qualifications in one class

Short read: Swinney: No proof of ‘explosion’ in multi-level classes

In four of East Dunbartonshire’s 10 secondary schools where almost all classes are taught on a single-level basis, only one uses tri-level teaching.

Most National 5 and Higher classes in schools on Orkney are single-level, but there are very few single-level National 4 classes.

In North Lanarkshire, however, all school have multi-level classes. One school stated that “almost all of S4 classes (with the exception of English and maths) are bi-level.” Other schools in the area protect single-level teaching for English and maths but make use of it for other subjects.

In Dundee, nearly 60 per cent of senior phase classes feature either two, three or four levels being taught in the same class, with bi-level teaching accounting for 47 per cent of total classes.

Both Glasgow and Edinburgh councils did not provide the requested information, while Clackmannanshire, Fife, Midlothian and Scottish Borders councils failed to respond to the request. Some others, such as Highland, Falkirk and Perth and Kinross, supplied incomplete responses.

In May, EIS union general secretary Larry Flanagan told MSPs that one of the biggest complaints from Scottish teachers was “the explosion in multi-level classes” whereby different courses, from National 4 to Advanced Higher, are taught in the same classroom by the same teacher.

He said that the growth in multi-level classes was “simply a pragmatic response to the limited resources that schools have to run the courses”.

Later that month, however, education secretary John  Swinney said that he had “not seen any data that would allow me to make a judgement about whether there has been an explosion or not, and I don’t think that data exists”.

A recent report by the Scottish Parliament’s Education and Skills Committee criticised the government’s lack of data on multi-level teaching.

And a recent survey by the Scottish Secondary Teachers’ Association (SSTA) found that  the “subject hierarchy” in national qualifications is being reinforced in multi-qualification classes, with teachers of “poor relation” subjects, such as art or design and technology, more likely to be asked to teach a range of courses in the same lesson than teachers of English or French.

The survey of more than 1,000 teachers has also revealed that they are not only being asked to teach multiple-qualification classes in S4 but also in S5.