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How Interleaving Works: Universal Strategies for Secondary School Classroom Practice

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An article by Richard James Rogers (Award-Winning Author of The Quick Guide to Classroom Management and The Power of Praise: Empowering Students Through Positive Feedback). This blog post is illustrated by Pop Sutthiya Lertyongphati.

Accompanying podcast episode:

In my twenty years of teaching, I’ve come across numerous pedagogical techniques designed to boost student learning, but few have been as transformative as interleaving. This technique, backed by cognitive science, has the power to enhance long-term retention and application of knowledge: yet it remains underutilised in many secondary school classrooms. Today, I want to explore generalisable rules for interleaving (a structured approach that any secondary school teacher can apply) and one that, to my knowledge, has never been formally outlined before. Out of all of the blog posts I have written to-date, this one has taken me the largest amount of time to research, collate and delineate. I hope that secondary school teachers everywhere will find this guide to be highly practical and transformative. A full bibliography of the research I have cited can be found at the end of this article.

What is Interleaving?

Let’s begin by first exploring this fundamental question: What is Interleaving?

Interleaving is a cognitive learning strategy that involves mixing different topics or types of problems within a single learning session, as opposed to traditional blocked practice, where students focus on one topic at a time before moving on to the next. Research suggests that interleaving improves students’ ability to discriminate between problem types, enhances problem-solving skills, and leads to stronger long-term retention (Rohrer & Taylor, 2007). As many of my readers will remember from an earlier blog post of mine, problem-solving is often a key characteristic of lessons in which deep learning (as opposed to surface learning) takes place.

From my own experience, I first stumbled upon the power of interleaving when preparing my Year 11 students for their IGCSE Maths exams. Rather than structuring revision lessons in the typical topic-by-topic format, I began mixing algebra, geometry, and statistics problems within the same lesson. Initially, students found this challenging, but over time, their ability to recall and apply concepts in different contexts improved dramatically. This worked particularly well when students had finished several topics during their revision sessions, prior to me bringing it all together within interleaved lessons.

The Science Behind Interleaving

Cognitive scientists suggest that interleaving works because it forces students to retrieve and apply knowledge in varied contexts, preventing passive learning and improving memory consolidation (Bjork & Bjork, 2011). A landmark study by Pan et al. (2019) found that interleaved practice led to better exam performance in secondary school students, particularly in subjects like mathematics and science where problem-solving skills are crucial.

Generalisable Rules for Interleaving in Secondary School Classrooms

Despite its effectiveness, interleaving can be difficult to implement without a structured approach. Based on research and my own classroom experiences, I propose the following generalisable rules for effective interleaving in secondary education:

#1: Mix, Don’t Isolate

Traditionally, subjects are taught in blocks, but interleaving requires deliberately mixing topics within lessons or across study sessions. For example:

In my experience, I have found that interleaving works best if you can connect the separate topics in some way, or if the topics themselves are closely related. In certain cases, project work in groups can lend itself well to interleaved exploration, provided that source material has been directly taught beforehand.

#2: Vary the Practice

Students should not only mix topics but also engage in different types of questions and formats. This can be achieved through:

#3: Space it Out

Interleaving is most effective when combined with spaced practice (also known as distributed practice), where content is revisited periodically rather than crammed in one session. This can be structured as follows:

For more information about the Spaced Practice Effect, and how to implement it (beyond the advice I have given in this blog post), then check out this excellent guide by Benjamin Keep.

#4: Scaffold the Difficulty

Interleaving is challenging, and students often find it frustrating at first. To ease them into it:

Scaffolding is an interesting and distinct domain of pedagogy in its own right and must not be ignored when designing an interleaved curriculum. Within a lesson, or sequence of lessons, my suggestion for good implementation would be as follows:

  1. Provide a quick starter: Use the Three As if you like, or these great starter activities.
  2. Use direct instruction, starting easy then gradually increasing the level of ‘cognitive load‘. Unfortunately, direct instruction has been tarnished with a bad reputation in recent years due to the move towards ‘student-centered’ learning, exploration and phrases such as ” Don’t be a ‘sage on a stage'” and “Don’t ‘spoon feed’ the students” being bandied around school staff rooms (I’ve heard them all!). However, the research suggests that direct instruction, especially when the teacher is mindful of Dual Coding strategies, has a significant and positive effect on learning outcomes.
  3. Go through interleaved worked examples.
  4. Allow students to work in small groups to complete mixed questions.
  5. Provide opportunities for independent practice.

#5: Explicitly Teach the Strategy

Students often resist interleaving because it feels harder than traditional blocked practice. However, just as with metacognitive strategies, we should be encouraging our learners to think about how they think. It’s crucial to explain:

Interleaving in Action: My Experience

When I first implemented interleaving, I noticed initial pushback from students. They were used to structured, predictable learning sequences and found interleaved practice to be more demanding. However, after just a few weeks, their ability to transfer knowledge across topics improved significantly. By the time mock exams arrived, they were better equipped to handle unfamiliar questions and apply concepts in novel ways.

For example, in my IBDP Maths AI class several years ago, I introduced interleaved problem sets that combined differentiation, probability, and trigonometry in a single assignment. Students initially struggled but later reported that the varied practice helped them identify links between topics: a crucial skill for higher-order problem-solving.

Final Thoughts: A Call to Action

Interleaving is a powerful, research-backed technique that every secondary school teacher should consider. While it may require a shift in lesson planning, the long-term benefits in terms of deep learning, retention, and problem-solving ability are well worth the effort.

In my book, The Quick Guide to Classroom Management: 45 Secrets That All High School Teachers Need to Know, I discuss how structuring lessons effectively can have a profound impact on student outcomes. Implementing interleaving is just one example of how thoughtful classroom strategies can positively engineer student success.

What are your thoughts on interleaving? Have you tried it in your classroom? Let me know in the comments!

Bibliography

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