Exam results are the most obvious method of measuring academic ability.

University admissions officers have long recognised, however, that the number and grades of Highers achieved at school is a crude means of assessing potential.

Does the middle-class applicant with a clutch of A grades and impressive extracurricular achievements merit a place when the would-be student with B grades from a school with low expectations and few family resources has had to study independently and may be more able?

All Scottish universities, mindful of a proud tradition of access to higher education on merit, are committed to offering more places to students from less affluent backgrounds. The main problem has been that the institutions with the largest intake of students with lower grades have the highest drop-out rates, reinforcing the view that exam results are the best indicator of future performance.

The experience over the past 10 years of Glasgow University's pioneering Top-Up programme confounds that. The nine-week access scheme for pupils from deprived areas in the west of Scotland widens their learning experience, assesses their potential and offers the possibility of entrance on lower grades. A study of 1000 students who were accepted via Top-Up found a smaller proportion dropped out between first and second year than those with better results from more advantaged backgrounds. It is even more encouraging that the drop-out rate is decreasing: in 2010, 12.4% of Top-Up students failed to progress to second year compared with 13.5% of their more affluent peers.

While this is undoubtedly good news, it is also undeniable evidence that in schools where few consider going to university able pupils are not being identified and helped to gain the necessary qualifications at an early stage. This a waste of talent and potential the country cannot afford, not least because successful students from poorer areas will have far more credibility in encouraging younger pupils to follow in their footsteps than any government or university initiative.

Nevertheless, measures to even out the playing field remain controversial. Universities which have recognised the extra challenges faced by applicants from more deprived areas by accepting them with lower grades have been accused of reducing standards. It is a particularly thorny problem for the most sought-after institutions, which must maintain their reputations against global competition but also widen access to retain Scottish Government funding.

All Scottish universities should take encouragement from Glasgow's Top-Up success because it shows that disadvantaged 17-year-olds have the potential to become graduates of the highest calibre. As Professor Anton Muscatelli, the principal of Glasgow University, points out, these students are more motivated than those who haven't had to fight to get into university and prove just as able, if not more so.

The lesson is that lowering grades by itself is not enough. Access programmes and mentoring schemes should now become the norm and extended as widely as funds allow if the potential of Scotland's young people and its universities is to be fulfilled.