Ahead of the ASCL Conference in Birmingham this weekend, there is a report in the press today about rising class sizes in secondary schools.

An analysis by teaching unions has suggested 62% of secondary schools have had to expand class sizes between 2014/15 and 2016/17. The study, conducted by the NEU, NAHT and ASCL – as well as non-teaching unions Unison, GMB and Unite – showed that of 150 local authorities, 83% saw a rise in average class sizes across their secondary schools, while 14% have seen a fall and 3% saw no change.

This report should come as no surprise to anyone connected with education. Indeed, I would predict that class sizes will continue to increase in size over the next few years as the secondary school population expands from its low point reached in 2014 and budgets also come under pressure.

However, there is an argument to be had about the usefulness of class sizes as a measure. They can be affected by factors such as the degree of non-contact time allowed to staff; policy over options at GCSE and for post-16 courses as well as space considerations.

An alternative measure is the Pupil Teacher Ratio. Even here there are now problems: how do you define a teacher. Do you only include those with QTS and exclude Teach First and School Direct trainees, as well as any other unqualified teachers or cover supervisors?

Anyway, I have included the changes in PTRs across different types of secondary schools since the School Workforce Census was introduced. The result confirms the findings from the unions and could have been researched without the need to waste valuable time in hard-pressed local authorities. As an added bonus, these are DfE approved numbers, so the government cannot quibble about them.

The big change has come since 2015 and probably reflects the loss of extra funding academies received in the early days of the Gove period at the DfE. The effect the loss of that extra cash has had on the funding of these schools is now obvious: sadly, once becoming an academy there is normally no way back. For that reason, heads gathering in Birmingham might want to examine the value for money of back offices at MATs.Source DfE SFR 25/2017 Table 17a

After all, it was the heads that complained for decades about the dead hand of local authority expenditure. Having been released from the frying pan of Local Authority spending patterns they must not fall straight into the fire of MATs with high relative overheads.

There are many other issues that secondary heads will need to consider at their conference. Perhaps one of the most pressing is finding the teachers to fill these classes that now have more pupils in them. It may be a productivity gain, but it does impose a greater workload on teachers and may the class size and PTR changes partly explain the growing loss of teachers with 3-5 years’ experience previously discussed on this blog.

In passing, the head teachers might also want to reflect upon the changing nature of the teacher vacancy market that helps provide the teachers. With the TES group reporting a loss of 2016-17 and the DfE working on a new vacancy platform, how teachers are recruited could become an important area for discussion over the next few years.

As one of the instigators of TeachVac, the free platform for vacancies, I am, of course, not an idle by-stander in this debate.