This is Interleaving: a Concrete Example

The Misconception

Interleaving has been under significant scrutiny recently on Edutwitter. A blog post from Jonathan Firth and a TES article from Mark Enser in particular have sent my mind spinning away on this topic.

Too many diagrams (like the one below), showing interleaving, create the misconception that you should teach different topics each consecutive lesson. This diagram was the first on a google image search for ‘interleaving learning’.

blocking cross


Interleaving’s aim is to create desirable difficulties (Bjork & Bjork, 2011) which aids longer term retention and also transfer to novel situations; both noble aims. However, planning out a curriculum calendar following the approach in the image would be horrendous, assessments wouldn’t happen for months (unless cumulative) and pupil absence could seriously damage their opportunity to learn key content.

As an example, lets assume the diagram above links to history taught two lessons per week. If a student is absent and misses the first time topic 6 is taught (end of week 2) they won’t be exposed to that content until the end of week 6! Beneficial?

This diagram of (supposed) interleaving looks more like a revision schedule set up to benefit from the spacing effect. It would probably make an effective revision program but surely wouldn’t be an effective way to initially deliver content. Or, more scarily, it suggests that you teach several different topics within one lesson… madness (for science anyway).

Interleaving or Interweaving

One key phrase which is coined with regards to a benefit of interleaving is that it promotes discriminative contrast. You are delivering content which has contrast to enable students to see the underlying principles across these different examples but this surely won’t happen if the content which is different is within different lessons.

I am about to start teaching a chemistry topic and the learning intentions have been set out in a traditional blocked fashion. See image below. Opportunities for discriminative contrast are unlikely to be particularly pronounced.

blocked approach

This topic concerning the different chemical properties of group 0, 1 and 7 will have been taught in this way, probably quite successfully, for many years. I’ve certainly delivered it like this. The lessons all show progression of depth of content, the learning intentions all escalate nicely through Bloom’s taxonomy and I could deliver all this using old lessons. Save myself some time. Tempting.

Below is an image of my interleaving (or interweaving – you decide) of the same content (I kept the colour coding to highlight the extent).


The Benefits

The aim is to deliver lessons focused more on conceptual knowledge within the different contexts across the broader topic creating desirable difficulties. The contrasts between the different groups are highlighted within each lesson and the depth of understanding of individual groups grows from lesson to lesson. Another lovely benefit of this approach is that if a student is absent for lesson two, they won’t miss out on group 1 (as they would in the blocked approach) because group 1 features significantly in lessons 3 and 4 and to some extent in lessons 5 and 6.

Students should also benefit from the spacing effect. The trend in reactivity for group 1 and group 7 is first encountered in lesson 2 and then revisited as part of explanations in  lesson 3, 5 and 6; the fact that they are in slightly different contexts in lessons 5 and 6 should help with transfer but the underlying principle governing the reactivity of elements is the same across all lessons concerning it.

Extra Challenge

At some point, once students have mastered the concept, I will challenge them to predict the trends in group 2 and 6. This should give me some idea as to how well the conceptual understanding has transferred. (I am REALLY looking forward to this!). When we revise pupils will complete flashcard and recall Q sheets over a period of about a week or so in lessons and for homework – I trialed this in the last topic with this class and it worked very well (see image below) – and I will use past exam Qs, which really do interleave content, to again see how well knowledge is being transferred and to focus on exam technique before the end of topic test.

Wish me luck everyone! (Oh, and Year 10 too. They probably need it more!)

recall imps

You can follow me on twitter @MrTSci409 if you like!



One thought on “This is Interleaving: a Concrete Example

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