The report on Kirkintilloch High in East Dunbartonshire described the quality of the curriculum as "weak overall" and said insufficient preparation for the major curricular changes had left some pupils poorly prepared for their national courses in S2.
Under its new headteacher, John MacDonald, the school had decided to move Standard grade and equivalent courses down a year, so that pupils choose their exam courses during S1 and sit their examinations at the end of S3 rather than S4.
Mr MacDonald said the school has started work on some of the issues raised and the inspectorate had already seen "the green shoots of recovery". The main aim of the change was to improve progression to National Qualifications, in order to raise attainment by the end of S5.
A similar move by Keith Grammar in Moray was taken to task by HMIE over insufficient planning. Glasgow City Council raised the stakes when it said all its 29 secondary schools should adopt a similar approach as a means of raising attainment - although some headteachers are understood to have reservations.
In the case of Kirkintilloch High, inspectors said the timescale for implementation had been too short, with the decision to change the curriculum having been taken only midway through last session. "As a result, staff had not been able to plan and prepare appropriately for courses or for the necessary changes to learning and teaching," inspectors stated.
"The timescale for implementing the major changes to the curriculum meant that many pupils were insufficiently prepared for their national courses in S2. A few S2 courses were set at levels which would not let pupils achieve their full potential at the end of the two years."
In other cases, teachers were having to adapt courses on an ad hoc basis as they were proved too demanding. "The school's evolving processes for monitoring pupils' learning experiences in S1-S2 were not sufficiently systematic or rigorous to support these changes," the report stated.
Almost all pupils follow nine Standard grade courses or equivalent in S2, although inspectors reported that "a number did not fully understand the course level at which they were working or the implications for progression beyond S3". There were no vocational options at S3-S4.