The Science of Learning, Simplified: Interleaving

In many classrooms, learning is organized in neat, predictable blocks. One skill, one lesson, one unit at a time. While that structure feels natural, research shows it may not lead to the strongest long-term learning.
That is where interleaving comes in.
Interleaving is a research-backed strategy that changes the way we traditionally sequence instruction. It can help improve student retention, strengthen problem-solving, and support deeper mastery over time.
Let’s take a closer look at what interleaving is, why it works, and how to use it in real classrooms without adding unnecessary complexity.

What Is Interleaving?

Interleaving is the practice of mixing different types of problems or topics during learning, rather than focusing on just one type at a time. This is often compared with blocked practice, where students work through many problems that all use the same skill.
For example, instead of solving 20 problems in a row on the same math concept, students might work through a set of questions that call for different strategies. This asks them to think carefully and decide which approach fits each problem.
It can feel more challenging in the moment, and that challenge is part of what makes it effective. Over time, students become more comfortable with the challenge and develop more flexibility to move between problems faster and more confidently.

What Does the Research Say?

Interleaving is supported by a strong body of cognitive science research, and its impact is both measurable and meaningful.
In a widely cited study, Rohrer and Taylor (2007) found that students who practiced math problems using interleaving performed significantly better on later tests than students who used blocked practice, even though they felt less confident during practice.
As the researchers explain:
“Although students who used interleaved practice performed worse during practice, they performed dramatically better on the delayed test.”
What feels easier during learning does not always lead to lasting understanding.
Brown, Roediger, and McDaniel (2014), in “Make It Stick,” reinforce this idea:
“Interleaving the practice of two or more skills… improves learning by requiring the brain to retrieve different solutions and discriminate between types of problems repeatedly.”
When students must decide what strategy to use, they move beyond memorization and into deeper thinking.

Why Interleaving Works

Interleaving strengthens learning in several important ways:
  • Builds problem-solving skills: Students learn to choose the right strategy, not simply repeat a familiar one.
  • Promotes deeper thinking: Mixed practice requires attention and analysis instead of automatic repetition.
  • Improves retention: Switching between concepts helps strengthen memory connections over time.
  • Encourages transfer: Students are better prepared to apply what they have learned in new situations.
In short, interleaving helps answer a critical question: Can students recognize when and how to use what they have learned?

How Teachers Can Incorporate Interleaving

Like Spaced Practice, interleaving does not require a complete overhaul. Small shifts in how content is structured can make a meaningful difference.
Here are a few practical ways to begin:
  1. Mix Practice Problems: Instead of grouping similar questions, include different types of problems within the same assignment or activity.
  2. Blend Old and New Content: Combine previously taught skills with current lessons so students revisit and apply prior knowledge regularly.
  3. Use Varied Review Activities: Design warm-ups or bell ringers that require students to use different strategies, rather than repeating just one skill.
  4. Ask “Which Strategy?” Questions: Prompt students to explain why they chose a certain approach. This strengthens decision-making alongside execution.
  5. Plan for Variety: When designing lessons or units, intentionally rotate between related concepts instead of teaching them in isolation.

Interleaving in Action: The Simple Solutions Approach

At Simple Solutions, interleaving is a core design principle. Our books are intentionally built to mix skills and concepts so students regularly engage with a range of content. This reflects how learning sticks best through repeated exposure, strategic variation, and ongoing Retrieval Practice.
Here is what that can mean for classrooms:
  • Stronger retention: Students move beyond pattern recognition and build real understanding.
  • Deeper mastery: Mixed practice helps students apply the right strategy at the right time.
  • Closed learning gaps: Regular exposure to multiple skills helps keep important concepts from fading.
  • More effective Tier 1 instruction: Built-in interleaving supports all learners and helps strengthen daily instruction.
  • Fewer students needing additional support: When students regularly work with mixed content, more can succeed the first time.
Our philosophy is simple. Real learning requires practice, and it also requires the right kind of practice.

The Bottom Line

Interleaving may feel less comfortable than more traditional approaches, but that productive struggle helps create lasting learning.
When students are challenged to think, choose, and adapt, they gain more than correct answers. They gain understanding.
And in today’s classrooms, that is the goal.
Interleaving may feel less comfortable than traditional approaches, but that productive struggle is what supports lasting learning. When students are challenged to think, choose, and adapt, they gain more than correct answers. They gain understanding.
Watch Our Spiral Review Webinar

If you would like to explore this approach more deeply, we invite you to watch the recording of our edWebinar, “Stop Reteaching: Close Learning Gaps with Spiral Review.” In the session, we share practical, Research-Backed insights on how spiral review can strengthen retention, close learning gaps, and support Tier 1 instruction in meaningful, manageable ways.