Last week news headlines announced that the number of children being home-schooled in the UK had risen by 40 per cent over three years (to 48,000). A report for the BBC’s Inside Out programme – recorded in Cornwall, where children and adolescent mental health services are particularly stretched – explored the idea that stress caused by education policy changes and increased examinations was resulting in children experiencing significant anxiety, to the extent that their parents felt they had no option but to remove them from school. This came hot on the heels of a shocking piece in the Guardian last month, which said that there were 43 schools in England alone which had a 20 per cent exclusion rate.

I spoke to the joint general secretary of the NEU teaching union, Dr Mary Bousted, who told me she thought it was "fair to say" that "more children than ever before are being excluded" and that "many of them have SEND". She said that the NEU is currently conducting a joint study with a university which will reveal exactly what proportion of excluded children come from low-income backgrounds or have emotional or behavioural difficulties. The results of the study are expected next year.

In the meantime, the consensus among teachers I have spoken to on the topic is that schools are being penalised for being inclusive. Emma Parker, who is the mother of a son with autism and ADHD who is currently being home-schooled, as well as being a primary teacher, placed the blame squarely on league tables. This was a view echoed by Giles Platt, a regional primary PE and PSHE adviser, who told me he thought children with mental health issues and SEND were being excluded around GCSE time because they would likely negatively impact exam results.

This might explain why Ofsted chief Amanda Spielman said during a Radio 4 interview recently that there was "no evidence" arising from Ofsted inspections that cuts to school funding had any tangible impact on the quality of education young people were receiving. Those hardest hit by the cuts are essentially invisible, since they are more likely to have been removed from school. Furthermore, if Ofsted inspections over the past five years haven’t reflected what is blindingly obvious to everyone else – that schools and the teaching profession are at breaking point and young people are suffering as a result – it would rather indicate that they are measuring the wrong things.

How can Ofsted measure wellbeing?

So, to attempt to measure pupil wellbeing or not to, that is the question? And it is one, I have discovered, which does not have as definitive an answer, as I had previously hoped…

You’ll often hear, on radio and TV interviews, calls for Ofsted to further increase its wellbeing inspection criteria, after having introduced some in 2015. (It should be noted, however, that these calls usually come from people who don’t work in education).

I, however, am wary. In 2016 I wrote a piece for the Telegraph looking at the way Ofsted measures rates of bullying in schools. I found that Ofsted essentially counted incidents of bullying in the school records, but there was no legal obligation on schools to record incidents. They were incentivised not to acknowledge them.

All schools have a "bullying problem" to one extent or another. The mere existence of bullying does not render a school "failing". What we deem an outstanding school in this regard should be one which has robust and extensive measures in place to resolve incidents and support both the bully and their victim.

In just the same way, the presence of pupils with mental illness and/or SEND should not reflect negatively on a school. Using this logic, if Ofsted, or another organisation, were to "measure wellbeing", they would, therefore, have to look at what the school had in place to support pupils, rather than attempting to measure the mental and emotional health of the student body.

After all, there are so many factors that might impact on pupil mental and emotional health which are outside of the school’s control. However, the ability of the school to provide, for example, an in-house counsellor, is entirely dependent on funding, which would likely again mean that the wealthiest schools would come out on top.

Additionally, wellbeing can be contingent upon so many fundamentally unmeasurable factors, like the relationship between a pupil and teacher, or whether one subject a pupil is studying (e.g., art or drama) is enabling them to explore and exorcise difficult emotions. The situation has something of the Schrodinger’s Cat about it, in that once you attempt to measure a mental health friendly-culture, it immediately changes the dynamics in such a way as to mean you’ll never get an accurate reading.

Ultimately, my fear is that any attempt to quantify pupil wellbeing would exacerbate the problem we currently have with exclusions. It would also undo so much of the work undertaken by charities and campaign groups to decrease stigma, since the message to young people would be that any mental health difficulties they might face would reflect badly on the reputation of their school.

Caroline Hounsell, psychotherapist and director of partnerships at Mental Health First Aid England, summed it up when she said that to penalise schools for mental health issues in pupils was "all stick and no carrot". The change that is required is deeper and more all-encompassing. The way schools are labelled and perceived, both by inspection bodies and within communities, needs to change.

Natasha Devon MBE is the former government mental health champion. She is a writer and campaigner, and typically visits three schools per week across the UK. She tweets @_natashadevon