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Prereq Checks – do they know what they need to know and how do we know?

This is a summary of the talk I gave on prereq checks at CogSciSci2022. If you bought a ticket, go watch the video when they get sent out – it has more detail and apparently I’m “very personable”. If you didn’t buy a ticket, why the heck not???

Before you start teaching anything new, it’s important to make sure your students have the prerequisite knowledge – that is the knowledge that is required to be able to access your lesson. If they don’t have this, there is no point continuing because without it they aren’t going to be able to properly understand what you’re trying to teach them. This is the foundations of the knowledge house you’re building, the concrete pad you’re going to start laying bricks on.

Do they know what they need to know?

What is it that they need to know? This is where your subject knowledge is very very useful. If your subject knowledge is secure, you can look at the topic you’re teaching and break it down into “pre-sub-topics” What are the bits that make up this particular thing I’m teaching? (I’m really trying not to use the word topic again). This is also where your curricular knowledge is useful – if topic A comes before related topic B, it’s a fairly good bet it’s because students need to understand something about topic A before they can understand topic B. Now, obviously this isn’t a hard-and-fast rule – sometimes topics come earlier because of reasons known only to whoever sequenced the curriculum, but in general, it’s a decent bet.

If I’m teaching the adaptations of the small intestine, this comes after the digestive system (year 4, year 8), and diffusion (year 7ish, year 9ish) – these are both related topics, and I can make a safe assumption that they come first for a reason. Something like reproduction (year 7) also comes before the adaptations of the small intestine, but it’s clearly unrelated, so I don’t need to worry about it.

How prerequisite is it?

Prior knowledge falls somewhere on a spectrum. Some of this prior knowledge is definitely prerequisite – if they don’t know this, they will really struggle to make any sort of meaning from what you’re teaching them. If they don’t know this stuff, you need to stop and you need to teach it to them before you continue. Some of it is probably not prerequisite (but is still useful stuff to know). This stuff you don’t need to teach them before you start. Other stuff falls somewhere in the middle and you could make the argument either way.

To go back to the example earlier, for students to be able to understand in any meaningful way the adaptations of the small intestine, they are going to need to have some concept of digestion, they are going to need to know what diffusion is. The way I teach this ‘lesson’*, my students will need to know the factors that affect the rate of diffusion. For other people, they might teach the adaptations in parallel with the factors affecting rate, and therefore the latter knowledge won’t be definitely prerequisite. No matter how you teach it, your students probably aren’t going to need to know about kinetic theory to access your lesson. Yes, it will help them make a deeper understanding, and it’s great if they do know it, and if you realise they don’t know it you should probably set them some retrieval homework on it, but if they don’t, you don’t have to stop your lesson to teach it.

How do you know [if] they know?

Ask them.

No really, ask them.

Get out your mini whiteboards. Make sure the pens work. Have a routine for handing them out and drill that routine. And then ask the students questions.

When checking prerequisite knowledge, you aren’t checking for understanding. You’re seeing if they know what you need them to know. Therefore, try to keep the elements of the question as limited as possible. You don’t want to ask a student a question that requires them to know and apply three different things, because if they get it wrong, you don’t actually know why they got it wrong – was it that they didn’t know X or Y, or maybe they couldn’t say how X and Y related to Z? That doesn’t help you to identify what it is the student doesn’t know. Of course, once you’ve ascertained a base level of prior knowledge, you can excavate further to see just where the edges of their knowledge is, but this isn’t your first port of call.

One thing that someone asked me after my talk was about asking them questions about things you’ve not personally taught them, and your expectations around that. Is it unfair to ask them questions that they might get wrong? No. No, it’s not. I’ve only been at my school since September, so there are lots of things I’ve not taught to my students, but that they will still need to know to be able to access my lesson. I need to know if they know those things. Assuming that they know them when they don’t will result in students not understanding what I’m trying to teach, whilst assuming that they don’t know them when they do will result in me wasting my time teaching them something they already know, and the potential for my students to switch off.

Anyway, once you’ve asked the question, they show you their whiteboards, the first place you look is your P students/lowest attainers/low ability/out of year group learners/struggling learners/whatever other euphemism you want to use. Basically you’re looking at the kids who get stuff wrong a lot. If they know it, it’s a safe bet that most other people in the class know it. You can never read all 30+ whiteboards – you need to sample – and sampling these students gets you good enough data.

You can also look at the students who generally get things right – if most of them get it right, there’s a chance this is something they’ve studied before, it’s just been forgotten by others, in which case you need to scaffold your explanation very carefully to make sure you’re bringing everyone with you. If your P students get it, but the higher attainers don’t, something’s gone wrong somewhere.

To conclude: don’t start teaching without making sure your students have the foundations you’re going to build on. Do this by breaking the topic into bits and working out what comes first. Ask questions that don’t require linking too many ideas so you get more data on what students know and don’t know. Feel free to ask those questions later to test the limits of their prior knowledge. Use MWBs.

*inverted commas because I’m talking about a lesson in the sense of a section of learning, as opposed to a period of specific length on my timetable. You teach it until they know it, not until the bell goes.


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