This year 22 per cent of pupils gained five or more Credit awards, against 11 per cent last year. The figure for five or more Credit and General passes stood at 70.6 per cent, compared with 50.7 per cent last year.
Rod O'Donnell, the headteacher, has attributed the improvements to streaming, the way the classes are resourced and the quality of teaching.
However, Mr Reilly has produced alternative figures which compare this year's results of the fully streamed S4 class with those of the final year of mixed-ability classes in 2002-03: Foundation - 91 per cent in 2002-03 and 89 per cent in 2005; General - 68 per cent in 2002-03, 71 per cent in 2005; Credit - 14 per cent, compared to 18 per cent.
Glasgow City Council, however, disputed his numbers. It said that the comparable figures for 2002-03 and 2005 for Foundation passes were: 91 per cent and 94 per cent; for General, 68 per cent and 74 per cent; and at Credit, 14 per cent and 22 per cent.
Phil Cairney, the school's Educational Institute of Scotland representative, said: "The streamed classes have their upsides: they are usually very well motivated. But the other classes, although usually smaller, can be challenging. However, it would appear that even the less able pupils are performing better."
Meanwhile, another school is claiming "incredible" success in exam results for pupils who sat their Standard grades in S3.
Dalziel High in Motherwell presented youngsters a year early in English and maths only, unlike Keith Grammar which had the whole year group sit the exam in third year (TESS, last week).
The Dalziel results show the two groups running almost neck and neck: 57 per cent of 175 pupils in S4 got a Credit pass in English and 40 per cent in maths, compared to 53 per cent of the 163 pupils in S3 who gained a Credit in English and 40 per cent in maths. Like his counterpart at Keith Grammar, Brian Miller, headteacher at Dalziel, spoke of the great opportunity for last session's S3 group to have a two-year run-up to sitting their Highers.
Mr Miller said: "I believe there is no reason to worry about Standard grade being dropped down a year. Over the next two years, we aim to allow pupils to start their Standard grade subjects in S2 and sit the exam in S3. This will also benefit S1-S2, where there has been concern about a lack of pace.
Since the course will now be confined to S1, there will be pace.
"While this is only the first set of results, it is a hugely important step which we are convinced will be replicated in the years ahead."