John Bald is a former Ofsted inspector and has written two books on the history or writing and spelling.

The Supreme Court put out a very strong team to consider the DfE’s appeal in the case of Jon Platt, the Isle of Wight parent who was issued with a fixed penalty notice for taking his daughter to Disney World in term time.

He was found not guilty by local magistrates on a charge of failing to ensure that she attended school regularly, and this decision was upheld in the divisional court, an unusual branch of the High Court in which two judges preside.

With this backing, Platt had some reason to believe he was in the right, and Lord Neuberger, who has been known to use sporting metaphors, duly put out what may be seen as his first team – himself, Deputy President Lady Hale, and Lords Mance, Reed, and Hughes.

Lady Hale’s judgment is clear, logical and instructive. The state of affairs it describes, however, is anything but.

The case turns on the meaning of “regularly”, an innocuous enough word until it is considered in terms of statistics, the real world, and legal precedent. Lady Hale and her colleagues say that it has “at least” three meanings – evenly spaced, sufficiently often, and “in accordance with the rules”, an interpretation more often seen in France, where a person avoiding a fare is described as being “in an irregular situation”.

An additional problem arose because the council had sent Platt a note stating that satisfactory attendance was 90-95 per cent, a level with which his daughter’s attendance complied even after the holiday. Platt, we may think, had some reason for believing that he was in the right.

The judgment’s account of previous decisions, dating back to 1870, seems to run pretty much in Platt’s favour until the final sentence in the section – “The answer to that problem could, of course, have been that “regularly” does not mean what everyone seems to have assumed that it means.”

What “regularly” means, according to this unanimous judgment, is “in accordance with the rules prescribed by the school.”  Given that the most important judgment in the Court’s history, on the referendum, turned on what parliament did and did not spell out – it did not make the referendum binding – it seems inventive to expand “regularly” into this phrase.

Could a school, for example, make Saturday attendance compulsory by writing it into its rules? Was the school in question subject to the rules of the Isle of Wight, which issued the penalty notice, and whose guidelines had not been breached?

The Prime Minister, in welcoming the judgment, said that:

“What the Supreme Court has done is endorse the current position… which is that we recognise – and they’ve recognised – the importance of children being in school and getting the most out of their education but also recognise that there may be exceptional circumstances where a child needs to be taken out of school during term time and it’s right that the individual headteacher has that flexibility to make that decision. I think that is the correct balance.”

Which brings me to two unsolved problems. The first concerns Ofsted, which has had to deal with statistics in determining levels of absence, and has found it difficult. Its first measure, of statistical significance, allowed attendance below 90 per cent to be discounted as not significant, and this was clearly wrong. Various other methods have been used since, with an increasing focus on the steps schools take to promote attendance and follow up absence quickly.

There is still room for unfairness. In 2006, attendance in a small school with which I was working was rated unsatisfactory because it had kept on its roll two pupils with cancer, as an expression of support for their families. Ofsted refused permission for the reporting inspector to make an allowance for this, and so made a judgment that it knew to be unfair as well as deeply hurtful to conscientious people.

Another case involving cancer was reported in the Daily Mail in 2015.  It takes a particularly stone-hearted and bone-headed bureaucrat to refuse permission for what may very well be a family’s last holiday together, and yet such people exist.

The Isle of Wight’s guidelines say that discretion as to what constitute exceptional circumstances should be exercised “sparingly”, and that is surely right. What is not right is to refuse every application as a matter of principle, without considering its merits. Now that headteachers have been given this power, parents need a channel of appeal in cases where it is misused.