My Year 8 class were being treated to a near-perfect history lesson, about the reasons for poor housing conditions in 19th-century industrial towns, when the interruption occurred.

I had kicked off with a tragic piece of storytelling about the death of a girl in Blue Bell Fold, Leeds, from cholera. That had led into an analysis of primary-source photographs of living conditions and then an assessment of more complex written sources. I was about to ask the pupils to select evidence to identify who was culpable for the innocent girl’s death - before debating the various suspects’ guilt - when a PE teacher walked in with a clipboard. Their aim was to observe my teaching, to judge this subtle, beautifully sculpted lesson. Inside me, a red mist began to descend.

“How dare they think they can even begin to judge this oeuvre! They probably couldn’t even tell me what cholera is. How could they begin to understand what is going on here? Who are they to judge me?”

Then came the shared internal thought of all observed teachers up and down the land - the urge to hand over the whiteboard marker and say: “If you know so much, you do it! Show me how it should be done.”

While the above scenario is a caricature, this reaction to being observed by someone outside of your own subject area will be more than familiar to many teachers. And now more than ever, it may appear justified.

GCSEs are getting harder and there is an increasing acceptance in secondary schools that subject knowledge is the key to great teaching. Twitter is awash with teachers declaring the primacy of subject knowledge and gimmicks such as “knowledge organisers” are seen as essential tools of the teaching trade. CPD providers, such as The Prince’s Trust, are offering courses focusing on precise areas of subject content, as opposed to the transferable fare of pedagogical techniques.

In this knowledge-focused climate, are the days of non-specialist senior leadership team (SLT) observations over? How can a teacher who has no understanding of a subject area really judge the teaching of a lesson?

My subject knowledge is at the heart of everything I do. I use it to identify what to teach, to decide what the significant learning outcomes should be, to select the most effective source material and resources, and to give specific feedback to the pupils on their journey to become active historians. If I’m observed by a subject specialist, I can receive feedback on how successfully I am doing this.

But since being placed within a larger humanities faculty, it has been a long time since I was observed by a subject specialist. I now receive feedback on the behaviour of pupils, my use of assessment for learning, and the pace and structure of my lessons. These are important aspects of teaching, but I yearn for feedback on my work as a teacher of history - not just as a classroom teacher.

Quality of teaching

So does that mean I only think subject specialists should judge my teaching?

Absolutely not. For starters, that would not make practical sense in the reality of the current system. Not every subject can have an SLT representative at the same time and county-based subject advisers are all but obsolete. A tiny number of multi-academy trusts have subject specialists advising across the trust, but rarely beyond the core subjects.

Secondly, teachers must face up to the reality that the people who manage schools need to know what the quality of teaching is like in the institutions that they run. High-quality teaching and learning must be the core aim of any SLT. To lead and manage this effectively, they need to have a realistic picture of what goes on inside classrooms on a daily basis. Whether teachers like it or not, this needs to involve classroom observations, work scrutinies and talking with pupils.

And thirdly, you don’t have to be a subject specialist to be able to judge great teaching. Having been an assistant head with responsibility for teaching and learning for the past four years, I have had the pleasure and privilege of observing many lessons across every subject. I would like to say that I am far better at assessing the quality of a history lesson than I am any other subject, but the truth is that great teaching is so obviously great teaching in any area of the school. It slaps you around the face.

Here’s the key: the person observing you does not have to be a subject specialist, but they do have to be a teaching specialist. I have a large catalogue of teachers and lessons with which I can compare any lesson I’m observing. Being on the SLT, I have also built up a broader picture of which teachers achieve sustained high outcomes, and what their teaching and learning looks like. I know the common strategies they use.

Yes, great teachers have strong subject knowledge; their passion for the subject, the expertise in explaining difficult concepts, their selection of subject material and their use of imaginative resources would be impossible without it. Yet great teaching is about more than just having strong subject knowledge. Many a teacher with a first-class degrees from Oxbridge have struggled at the chalkface. Rich and deep subject knowledge, and how to convey that knowledge, are the key ingredients of a great teacher.

So embrace those SLT observations and respect them for what they are. Yes, the observer might not know that during the Battle of Waterloo in 1815, Napoléon Bonaparte was suffering terribly with piles, but they will know enough about teaching to help you become a better teacher.

If you feel that your lesson cannot be understood without some subject knowledge, then educate the observer. My favourite lessons to observe are those in which the teacher comes up to me the minute I step in through the door and tells me exactly what learning is happening and why. Alternatively, give the observer some background reading to do before the observation.

But this is not a free pass for the SLT. Senior leaders must never underestimate the impact of deep subject knowledge on great teaching and learning. They need to try to find the resources to ensure that subject knowledge is a sustained focus of any CPD programme. They also need to appreciate that deep subject knowledge is the iceberg under the surface of a great lesson - and you are only seeing the tip.

John Stanier is assistant headteacher at Great Torrington School in Devon