I look back now over my 15 years of headship and realise just how boring I must have seemed. Every new school year I’d say pretty much the same things to the staff and to the students. I’d reaffirm in our opening staff meeting and in those first assemblies our basic shared expectations of behaviour, of courtesy, of the way we were all – adults and young people – expected to conduct ourselves.

And with the staff I’d often use the same tedious formula:

“I know that none of us went to university in order to spend time telling students to take their coats off, to put their bags on the floor, to put their pens down when we are talking, but if we get these small details right, then we establish clear boundaries of how we behave in our school.”

I’ve been thinking about this because there have been confusing reports in the media about schools and behaviour.

On the one hand, the use of exclusions, suspensions, isolation rooms and that new-found term "off-rolling", seem to have been bundled up into a narrative that schools are being too strict, while on the other hand, some commentators appear to want greater strictness through measures such as a blanket ban on mobile phones.

This badly needs some disentangling.

Let’s be clear from the outset that exclusions and off-rolling are entirely different. Exclusions are a legitimate sanction used to maintain a climate conducive to learning. Off-rolling is the unethical and illegal practice of encouraging pupils to leave a school in order to massage performance tables. There is anecdotal evidence of a small number of schools off-rolling pupils, but it is not remotely the case in the vast majority of schools, which deplore such behaviour.

Exclusions are not taken lightly. Schools have to follow procedures set out in statutory guidance which, in the case of a permanent exclusion includes a duty for governors to review the decision and a right of referral to an independent review panel. The perception that may have formed in some minds of some sort of exclusions free-for-all is at odds with the reality of processes which have to be painstakingly followed.

That does not mean that we are taking issue with the Department for Education’s decision to commission a review of school exclusions, or the work of the House of Commons Education Committee in this area. It is clearly right and important to fully understand why there are differences in exclusion rates in different areas of the country and why some groups of pupils are more likely to be excluded.

Our point is that the answer to these questions is likely to be complex and nuanced and that schools are not kicking out pupils on a whim.

The fact is that the appropriate use of exclusions, both on a fixed-term basis, and, in a small number of cases, permanently, is an essential part of school discipline. Which brings me back to that formula I trotted out to staff each year about establishing clear boundaries for behaviour.

You have to have some collective lines in the sand, some behavioural non-negotiables that every adult – not just every teacher – subscribes to and insists on and enforces, whether they agree with them or not.

Back in my years of headship we quickly agreed that a student who was disruptive or defiant had to be removed from the lesson. We owed it to the teacher to do this and to the other students. The symbolism was also important – deterring others from falling into patterns of bad behaviour by seeing that there was a clear consequence of behaving badly.

Thus, we had a specified room where any student who behaved badly would be taken to work in silence, supervised by a senior member of staff. There might be a handful of students in there on any given day. They’d work without talking, have their lunchtimes separate from the rest of the school, and be expected to apologise to the member of staff whose lesson they had disrupted.

Very occasionally, you’d encounter students so out of control that they’d lash out and refuse to attend the isolation room.

So where precisely do you go from there? I was always clear in response to that. If internal isolation didn’t work, then the next step was a fixed-term exclusion. That meant the child being kept at home, and only returning to the school when an interview with the parent or carer had taken place and an apology received from the pupil.

And with some young people – a few who were so violent, disruptive and threatening – then there was no alternative but to exclude them permanently. For some, a fresh start in another school was what they needed; for others, an alternative provision with more adult support, smaller classes, and a bespoke curriculum was the best solution.

I imagine many schools will have a similar approach to the one that we used, and I imagine also that it would be supported by most parents and carers because they want their children to be taught in a well-ordered environment. This issue, of course, comes down to a matter of balance between the need for appropriate sanctions and ensuring they are not used excessively. My experience is that schools generally get that balance right.

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