Can you know something and not understand it? Yes. For example, you might know that:

• The USA has a right to silence under police questioning, where people are said to be ‘taking the fifth’. (* see comments!)
• That climate change is happening and burning fossil fuels are a part of the reason.
• That a puddle evaporates more quickly on a sunny or windy day.
• That ‘Full of scorpions is my mind, dear wife’ is something Macbeth says to Lady Macbeth after he’s killed Duncan
• That livings have changed over time by a process called evolution.
• That the rules for trig can be remembered by SOHCAHTOA?

In each case, the knowledge you have can be partial to the extent that you know that these things are factually accurate but you couldn’t answer the question ‘why?’ You might recognise and even assert that these statements are correct but you couldn’t explain them to someone else. On that basis, you can’t say you understand them. In order to understand them, you don’t need some kind of mysterious form of special insight; you need more knowledge – the type that gives reasons, forms connections and links the ideas back to some fundamental principles or widely understood concepts.

There are two powerful ideas from Dan Willingham that I find I refer to repeatedly:

• Understanding is remembering in disguise.
• Understanding can be thought of as the capacity to explain.

Using these ideas together, when we are testing students or students are testing themselves – when we are engaged in checking for understanding – it makes sense to frame this as testing students’ capacity to explain, from memory. The challenge is to do this well, in varied ways, and to involve all students – as explored in these earlier posts:

Giving an explanation is a very rich form of retrieval practice. It requires students to know basic facts and terminology, to understand how a sequence of ideas link together in an explanatory narrative and to apply this knowledge to a specific context. It’s a great test of understanding, not least for the person giving it – if you try to explain something you can get a good sense of what you understand yourself. If, as a teacher, you ask two or more people to explain something, you get to hear different versions, revealing different nuances or gaps in the way ideas are expressed. This is something I find every single time I ask my favourite CPD question: Why does the sun rise in the East?

What I think teachers could do more of, as part of a diet of retrieval practice and checks for understanding, (based on my observations over the years) are lessons where all students get a chance to explain ideas; to give an explanation. This can make many forms:

• Cold calling with probing questions, where students are given time to explain something in full, perhaps via a series of probing questions directed to them, before the baton is passed to another student
• Telling the story: students running through an explanatory narrative that links one idea to the next, including casual connections, visual and mental models.
• Think Pair Share, where students rehearse and then give a full explanation.
• Paired checks for understanding where one student explains to their partner who is equipped with a knowledge-check resource to support verification and a check for completeness
• Instructional inputs where individual students delivering planned explanations, explaining ideas or solutions to questions to the rest of the class.
• Written or verbal explanations as part of short-cycle feedback loops: everyone writes or delivers a short explanation, using diagrams as needed and then shares it, possibly by reading them out. The teacher gives some general feedback and then students re-do their explanations, adding depth and detail – they practise giving their explanations, getting better at doing it and becoming more confident in their knowledge.

Of course, this can’t all be done at once -it’s about mixing things up over time, much as described in this post, where teachers choose between mini whiteboards, cold calling and talk partners, and other techniques as needed.

In conjunction with these approaches is a teacher’s mindset not to accept simple repeated ‘off pat’ statements as a proxy for a full explanation. There needs to be a degree of generative thinking – students selecting, organising and integrating information, applying general ideas to specific contexts and scenarios. It also helps to embed and celebrate this way of thinking with students: beyond ‘do you know it?’, the focus should be ‘can you explain it?’ For students themselves, from ‘do I know it?’ to ‘how well can I explain it?’

Crucially, to reference a common weakness I see on my various school visits, teachers need to consciously explore students’ knowledge and capacity for recall far beyond simple quiz-based knowledge testing. This has its place but on its own is simply not enough. To re-emphasise the point of this post, you can’t really tell if a student knows something well unless they’ve had a chance to explain it. So – an important part of planning a lesson sequence is to ensure all students have opportunities to do the explaining.