It’s 15 minutes into the lesson and the students have all finished their DIRT time. Their purple correction pens are returned to the box at the front of the classroom and the main activity of the lesson has begun.

The teacher is explaining a new concept to the class, who are interacting via a mixture of cold-calling and hands up. Five minutes later and the majority of students are engaged in active learning. There’s some nice "think, pair, share" discussion happening and, as I circulate, I question a few students as to whether they are clear on the task they need to complete and the extent to which this links to their previous learning.

One boy stifles a giggle as I ask him something about the stoichiometry topic that they are studying. Possibly the question I have asked is really obvious to him or it might have been my amateur pronunciation of the word. He clearly explains the steps that he needs to take in order to complete the problem. He understands the content and has reasonable subject knowledge whereas I, the person watching the lesson, do not.

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That’s because, as an English teacher, Year 10 chemistry is about as far from my comfort zone as I can get. And, as an observer, I happen to think that is a good thing.

As a secondary school teacher, if you do happen to be awarded the luxury of time to observe other colleagues, then most stick within their own department. The idea is that you are able to assess teacher subject knowledge alongside pedagogy.

While I can see the rationale behind this, it is not always the most effective training for either the observer or the observed. In fact, I would contend that we learn the most from observing outside our subject specialism.

If I watch a colleague teach content that I am very familiar with, then, at the back of my head, I am always thinking about how I might teach that topic myself. It is very difficult to step away from familiar subject matter.

Also, as a line manager, I am usually considering a wealth of other factors at any particular time: is this colleague likely to pass their NQT year? Will they get through the exam spec in time? Should I put them on A level next year?

Observing outside your subject takes away the noise.

Better lesson observations

But if you can’t assess subject knowledge, how useful will your feedback really be? I would argue that, actually, my feedback will be more valuable because I don’t understand the content of the lesson.

For one thing, it puts me in a similar position to one of the least able students in the class, so I can really assess how clear the instructions have been.

Recently I observed GCSE French, having not been in a French lesson since I was in Year 9. The clarity that I felt as an observer was very enlightening. Without a clue as to what was going on (the lesson was in French), I was able to concentrate on the body language of both the students and the teacher. I was able to think more closely about timings. I could assess the amount of thinking time that was being given to students.

In other words, I was far more interested in the pedagogy than the subject.

Also, giving feedback to colleagues about a subject that you have no expertise in forces those conversations into a more useful direction. As the person giving feedback, you are more likely to ask questions about the rationale behind a task or the way in which the teacher might do it differently in future if you are not full of ideas yourself.

And if we argue that feedback conversations should be driven by the person who was observed, then having an observer from another department will increase the likelihood of this happening and will, ultimately, make the process more helpful.

There are huge benefits for the observer, too. After watching that French lesson and having a subsequent conversation about cold calling, I spent all of my lessons the next day focusing specifically on no hands up and giving students waiting time. It was a little tweak but I’m going to keep working on it.

Likewise, I saw members of my own Year 9 class really being pushed with some probing questions in geography and it made me rethink my own types of questioning for that particular group.

It really is a win-win. So why don’t we do it more?

Katherine Burrows is an English teacher at Abingdon School in Oxfordshire