Mary Curnock Cook warns that in a world of competition, grade thresholds have become moving targets

For the second year in a row, A-level grade deflation grabbed the headlines on results day. Leaving aside the question of whether or not this is a good thing, the small reported changes – the proportion achieving A or A* fell by 0.3 percentage points – translate into significant impacts for those working in university admissions.

Apparently tiny percentage point drops in the grades achieved are magnified when applied across a portfolio of three A levels. Thus we can estimate that this year 5 per cent, or 2,000-3,000, fewer than expected school leavers have achieved A-level grades of ABB or better.

It might be easy for politicians and awarding body chiefs to brush this off, but the results could leave 30 or so higher education institutions with at least 100 fewer ABB+ recruits than expected. No wonder many of the top universities had vacancies for adjustment and clearing this summer. No wonder several universities will be softening their target entry tariff for 2013-14 – after all, it is not the potential of these students to succeed in higher education that has changed, only the grades they are starting with.

According to some national news reports, a shift towards “harder” subjects has caused the drop. This is somewhat puzzling. I thought the A level itself was supposed to be a common standard. Ah yes, I hear you say, but we all know that isn’t really true. Surely mathematics is harder than psychology? The answer to such questions isn’t straightforward. Many of the so-called “harder” subjects (mathematics, chemistry and so on) have always returned much higher proportions of A/A* grades – for example, 43 per cent A/A* for maths compared with 17 per cent A/A* for psychology. A shift towards more students taking these “harder” subjects could not, therefore, produce the overall deflation effect that has been reported.

Confused? So am I. Not least because no one has ever done a decent analysis of the A-level data published by the Joint Council for Qualifications each year. Nor has there ever been a serious debate about why comparative standards produce such different outcomes across subjects.

Whether or not small changes in A-level results are a good thing, they can translate into significant impacts for those working in university admissions

And the gruesome tables of A-level results by subject published by the JCQ each year on results day have been set out in the same format for decades, despite significant changes to the patterns of entry over that period. They don’t tell us how many people took A levels, nor the average number per student. They say nothing about subject mix or the more recent practice among students of mixing A levels with vocational qualifications. And they make no attempt to look at the rate of study within the population for different subjects (a rise in the number of people taking a subject is not the same as a rise in its proportional popularity among the cohort sitting A levels).

Among A-level candidates who apply through Ucas, early data indicate that there are discrepancies between this year’s results, achievement at GCSE two years earlier, and predicted grades. This also happened in 2012; hence the surprise at last year’s quite large drop in AAB+ achievements at A level, which left several universities with a shortfall in student recruits.

But it looks as if vocational qualifications, particularly BTECs, will partly come to the rescue of universities seeking to recruit ABB students. If it seems to be getting harder to get ABB at A level, it is becoming easier to do so through BTECs – at least if we use earlier attainment at GCSE as an indicator of difficulty at Level 3. Pearson, the company that owns the BTEC qualification, recently published results showing that the proportion of learners achieving the top grades (D and D*) had risen by 3 per cent since last year. While a 3 per cent inflation of top grades at A level would have been a national scandal, vocational qualifications remain steadfastly below the political and public radar, despite their continuing rise as an alternative to A levels. More than 100,000 of 2013’s Ucas applicants now hold BTECs.

In the end, none of this should matter to anything other than the (important) debate about the outcomes of secondary education for young people. In English higher education admissions, however, there is now no cap on the number of ABB+ students that a higher education institution can recruit, making such trends of consequence. Different grade awarding trends for the two main university entry qualifications, A level and BTEC, mean that proportionately fewer A-level applicants are exempt from controls on student numbers, while proportionately more BTEC applicants are getting over the ABB+ threshold.

You may or may not think that this trend is desirable. But it is very clear to universities trying to manage their admissions in a newly competitive market that the ABB threshold has become a moving target.