The need to save money by cutting spending has driven council decisions to abandon the cap on S1-2 class sizes for English and maths.
Highland Council, which took its decision last month, is a case in point. By scrapping class sizes of 20 in early secondary, the authority was able to cut 38.5 full time teaching posts and save pound;1.5 million over two years.
In total, Highland councillors agreed to cut 300 jobs over the next two years to save pound;17.8m. Education was one of the worst hit departments, with around 80 jobs set to go. The council, however, still needs to find another pound;17m of savings.
Midlothian also scrapped the target because of "financial constraints". By returning to class sizes of 30, the council estimated it would save pound;289,088 this year and pound;462,540 next year.
In Fife, it was decided as part of the budget last February that class sizes in English and maths in S1 and S2 be allowed to rise to 25.
East Ayrshire Council also confirmed it had abandoned the policy of maintaining class sizes of 20 in English and maths. Average class sizes in S1 and S2 were between 25 and 28, although in some schools they could rise to 33 or drop to 18, said a spokeswoman.
East Lothian Council said it had never adopted the policy in the first place.
Meanwhile, there are three authorities where class sizes of 20 are hanging in the balance: Orkney, Moray and Angus.
Angus said the target remained council policy "at least for the current year"; in Orkney, no decision has been taken on whether the policy would be maintained; and in Moray it is being considered as a budget cut this year.
Moray Council was currently spending pound;500,000 to maintain low class sizes in English and maths, said a spokesman, but this could change when it sets its budget in February.
Larry Flanagan, education convener of the Educational Institute of Scotland, claims that reverting to class sizes of 30 will be to the detriment of pupils.
Ann Ballinger, general secretary of the Scottish Secondary Teachers' Association, describes the difference between teaching a class of 30-plus and one of 20 as "enormous".
"Larger class sizes simply make it much more difficult for teachers to pick up on pupils who may be struggling quietly in a corner or who may need to be stretched. It is a great pity that so many councils are turning their backs on this policy," she said.
HMIE has consistently made the point that S1-2 is the phase of education that "adds least value to the progress and achievements of many young people".
S1-2 CLASS SIZE TARGET FOR ENGLISH AND MATHS
NO TARGET OF 20 PUPILS PER CLASS
Argyll and Bute
IN THE BALANCE
POLICY STILL IN PLACE
Dumfries and Galloway
Perth and Kinross