Not for the first time, the Higher English examination is under scrutiny. As The Herald reveals today, the Headteachers' Association of Scotland (Has), has launched an investigation into discrepancies between grades awarded to candidates in the prelim and the award secured in the final exam. The association, which represents secondary heads, was prompted to act after anecdotal evidence of "surprising" differences between a candidate's predicted grade (based on performance in the prelim) and actual award given. Concern has been expressed in the past two years about pupils doing less well than predicted, sometimes markedly so. In some cases performance was better than expected.

Not for the first time, the Higher English examination is under scrutiny. As The Herald reveals today, the Headteachers' Association of Scotland (Has), has launched an investigation into discrepancies between grades awarded to candidates in the prelim and the award secured in the final exam. The association, which represents secondary heads, was prompted to act after anecdotal evidence of "surprising" differences between a candidate's predicted grade (based on performance in the prelim) and actual award given. Concern has been expressed in the past two years about pupils doing less well than predicted, sometimes markedly so. In some cases performance was better than expected.

According to HAS, the Scottish Qualifications Authority (SQA), this country's exams body, does not believe there is sufficient evidence to warrant the level of concern. That this is is a potentially serious matter is demonstrated by the fact that HAS has taken the highly unusual step of holding its own inquiry. It does not do such things lightly. It is worth recalling that the representations of its then membership played a major part in the review of upper secondary schooling which resulted in the Higher Still programme of courses and awards for 16-year-olds and 17-year-olds.

It is too early to know whether this latest initiative will result in further changes to Higher English, which has already been the subject of review and change since Higher Still was introduced. If any exam needs to enjoy credibility and confidence, it is Higher English. It is the most important subject. The Higher figures on the list of requirements for entrance to each university course. If there are inconsistencies in marking, as anecdote suggests, these need to be removed, not just for the standing of the award but also to ensure no young person loses out because standards are not in harmony across the country.

Consistency is more difficult to achieve in a subject that involves an element of subjectivity in the marking process. To take account of this, there is a set scheme for markers and they are graded, the purpose being to ensure no candidate suffers from marking that is harsh, or, indeed, gains if it is lenient. Yet the intervention of HAS suggests that the system does not work as well as intended.

Higher English is a "big bang" exam, with the award predicated on performance on the day. The exam has two parts, close reading (or interpretation) and literature. Examiners are looking for candidates to give answers that not only demonstrate they are skilled in analysing the text but also that they can express themselves clearly, fluently and formally. It is right to frame the exam in a way that ensures candidates cannot parrot the answers. Consistency in marking is challenging in these circumstances but it must be achieved. Given the subject's status, a fail or a poorer than predicted grade can be the difference between acceptance for a university course and rejection. There is no case for ringing alarm bells about Higher English. But the HAS investigation is warranted. It should also examine whether the prelim grade is the best predictor of performance in the Higher, given that it comes earlier in the year when teachers have not taught the full course.