No subject attracts quite so much attention in education news at the moment than the increased rate of exclusions. And over the past few days they have been blamed as a factor in the appalling and tragic rise in knife crime.

Home secretary Sajid Javid was quoted in the The Daily Telegraph as saying: “The number of exclusions we are seeing all seem absolutely to be heading in the wrong direction.”

And the Department for Education said darkly that a legal mechanism to hold schools accountable for excluded pupils was “not off the table”.

The popular perception seems to be that schools are excluding pupils willy-nilly and – when they cannot kick them out through official processes – illegitimately off-roll them on an industrial scale to boost their position in league tables.

So, let’s look at the numbers. In 2016-17 – the most recent statistics – the rate of permanent exclusions across all state-funded primary, secondary and special schools was 0.1 per cent of pupil enrolments, which is equivalent to around 10 pupils per 10,000.

And this is what the Department for Education’s statisticians tell us about the trends: “Looking at longer-term trends, the rate of permanent exclusions across all state-funded primary, secondary and special schools followed a generally downward trend from 2006-07 when the rate was 0.12 per cent until 2012-13, and has been rising again since then, although rates are still lower now than in 2006-07.”

It is hard to reconcile these figures with the current depiction of some sort of wild west scenario regarding exclusions.

Even if we look at secondary schools in isolation – where the largest number of exclusions occur – the figures are hardly on an epic scale. “The rate of permanent exclusions in secondary schools increased from 0.17 per cent in 2015-16 to 0.2 per cent in 2016-17, which is equivalent to around 20 pupils per 10,000,” the statisticians tell us.

Should we be worried about these figures? Of course, we should be. Any decision to remove a child from a school is an incredibly serious matter. The rise in exclusion rates is clearly a matter of legitimate and proper public concern. But we need to retain some sort of perspective about the numbers involved.

The statistics tell us what we would expect; that decisions to permanently exclude are rare. Schools are not full of trigger-happy headteachers turfing out pupils at the drop of a hat, but professional, committed individuals who make this difficult decision only after much thought and soul-searching.

And they do so not to manipulate league tables but because they have a duty to all the pupils and staff in their schools who have a right to learn and work in a calm and safe environment.

There has to be a point at which the behaviour of a pupil is so persistently disruptive or a risk to others that their continued presence at the school is irreconcilable with the best interests of the wider school community.

And an exclusion which is properly conducted according to laid-down and detailed procedures may actually benefit the pupil who is excluded by giving them a fresh start in a new school or a place in alternative provision where there is a high level of tailored support.

The million-dollar question then is why are we seeing an increase in exclusions? In fact, on this occasion, that cliché is particularly apposite. Because this is a question of money. The rising number of exclusions correlates almost precisely with the squeeze on school funding.

A coincidence? Not from what our members tell us. What we hear about is the heartbreaking cuts many have had to make to pastoral support, classroom assistants, educational psychology, and all the other services for vulnerable children.

Some of those children have challenging behaviour which requires early intervention and with school budgets under such pressure that becomes more and more difficult. Alongside that is the cutbacks we have seen to the support in the community to local services for vulnerable families. The result is that our schools serve many troubled, fragile children, and don’t have enough money to provide them with the support they need.

So, what is more likely to be behind the rise in exclusions? That headteachers who enter the teaching profession because they believe in the power of education to improve our society are arbitrarily abandoning their principles? Or that a massive system-wide crisis in funding levels and a decade of austerity is to blame?

That’s not to say that there are not some – a very small number – who are behaving unethically by off-rolling pupils. We read and hear the stories about schools "encouraging" parents to remove their children before they are excluded. But the reality is that such practices are abhorred by the vast majority of school leaders and are not remotely representative of the strong ethical core which runs through most schools.

And, finally, on that point about the tenuous correlation between exclusions and knife crime there are perhaps two points to be made. The first is a study of the educational background of young knife possession offenders by the Ministry of Justice last June which found:

“Only a very small proportion committed the knife possession offence shortly after being excluded from school. For those with a permanent exclusion that came later than their knife possession offence, half were excluded within the next 30 days. Although it is not possible to identify from this analysis whether there is an association between exclusions and knife possession offending, the low volumes of knife possession offences following exclusions mean any such association could not be a significant driver of youth knife possession offending overall.”

And secondly, isn’t it much more likely that the biggest factor in the rising incidence of knife crime is the fact that the number of police officers in England and Wales has dropped by just under 20,000 since 2010?

So, yes, we need a reality check about exclusions.

But let’s not allow the topic to become an easy distraction from the far more pressing issues of law and order, social cohesion, and – most urgent of all – the woeful under-funding of our public services.

Geoff Barton is the general secretary of the Association of School and College Leaders