A Teacher’s Guide To Spaced Repetition And Creating An Effective Spaced Repetition Schedule

Spaced repetition is a memory technique with a potentially powerful effect on classroom learning and memorization of information.

This article introduces the concept of spaced repetition, examines how it complements other areas of educational research and provides practical advice for teachers to take advantage of this spacing effect in the classroom.

What is spaced repetition?

Spaced repetition is the process of learning new material and reviewing it across multiple learning episodes over a period of time, optimizing long-term retention. This prevents the need for re-learning or cramming before tests which may cause test anxiety.

Experimental psychology shows that learning improves when students revisit and review new material over spaced intervals throughout the academic year. It is often referred to as the spacing effect.

Why is spaced repetition an effective learning strategy?

Neuroscience shows spaced repetition is an effective learning strategy and study technique because each time students recall information from long-term memory, it strengthens the neural connections associated with that piece of information. 

This makes retrieval practice easier later, even months after the initial teaching, and may eventually become automatic. With recall, reinforcement, or review, students remember more information.

Ebbinghaus’ forgetting curve

In the late 19th century, German psychologist Hermann Ebbinghaus conducted learning and memory experiments on himself. He discovered that soon after the learning of new information, these memories decay quickly and then at a slower rate over time. 

His experiments demonstrate that people forget most newly learned information unless reinforced.

Ebbinghaus forgetting curve

Spaced repetition combats the forgetting curve

Spaced repetition research shows that the memory decay rate decreases significantly when recalling, revisiting or relearning information. This pattern continues for each subsequent revision and retrieval practice session.

Distributing the practice of new material for two weeks after the initial learning and scheduling review sessions for one and two months after learning can help students remember almost all of the information.

A graph showing more knowledge retention with spaced practice

Classroom settings support the effectiveness of spaced repetition algorithms. For example, Rawson et al. (2013) found students who reviewed new vocabulary over several sessions performed better on a test immediately after studying and again four weeks later. This was compared with students who revised for the same time but in one single session.

Spaced repetition techniques

Now that you understand the principle of spaced repetition and why it is effective, let’s consider the learning techniques and teaching strategies that use spaced repetition.

Active recall

Active recall is retrieving information from long-term memory without using cues. For example, a ‘filling in the blanks’ exercise is only an example of active recall if there’s no list of missing answers. Flashcards only provide learners with active recall if they answer the questions (out loud or written down) before turning over the cards.

Spacing out opportunities for active recall is one of the most effective study methods students can adopt to strengthen the connections in long-term memory.

Leitner system

Leitner developed a system to provide students with the best-spaced repetition experience for using paper flashcards. The simple system organizes flashcards into boxes or compartments based on how well a student has memorized or mastered the topic on each flashcard.

Each compartment is ordered according to the amount of time required between the current retrieval and subsequent retrieval to memorize the information on the flashcard. 

Flashcards remembered perfectly move into the next compartment. This means there will be a longer interval between retrievals. Flashcards remembered less well remain in the same compartment, giving less time between retrievals. Incorrectly answered cards move to a compartment for more frequent review.

This approach is simple to implement and gives students ownership over their spaced repetition learning. 

In addition to flashcards, this learning technique can apply to short multiplicaiton tests or past paper questions.

Repetition schedules

It is important to consider how long the time intervals are between study time and retrieval attempts when designing a spaced repetition system (SRS). Intervals should be short after initial learning and then as long as possible without jeopardizing the learning process.

It is impractical for students to review all learning continually at short intervals; there must be a balance between workload and effectiveness. Many spaced repetition apps support students and teachers with this dilemma, including SuperMemo which arose from research conducted by Piotr Wozniak. This spaced repetition software calculates the optimal time intervals between retrieval attempts based on the learner’s previous performance and the complexity of the task.

Spaced repetition in the curriculum: how it works

Although spaced repetition is an effective independent revision strategy, it works equally well when incorporated into the scope and sequence or syllabus.

For example, teachers could arrange for each homework to include questions from previously learned topics so that students revisit each topic at least twice every term. 

The concept of a spiral curriculum is based on the spacing effect. Spiral curriculums review and revisit topics repeatedly throughout the year, increasing the complexity level each time students review a topic. 

When writing assessments, teachers can interleave previous topics in with the new ones. For example, the assessment may test area and perimeter, but present the lengths as fractions to revisit adding and multiplying fractions.

How to create an effective spaced repetition schedule

One of the simplest ways to create a spaced repetition schedule that will benefit all students in the class is to incorporate it into the existing scope and sequence.

Introduce each new topic into a ‘spaced repetition’ column in the scope and sequence at the following time intervals relative to the initial teaching:

• One week
• Three weeks
• Six weeks
• Ten weeks
• Fourteen weeks
• Eighteen weeks

The spaced repetition column in a scope and sequence will prompt teachers to review the previously learned material in some format. They may do this through homework, a low-stakes quiz, or interleaving it with the week’s new topic.

Although beneficial, creating personalized spaced repetition schedules for students is a lot more time-consuming. After each retrieval attempt, schedules need adapting. Supporting students to use the Leitner system independently is an effective way to solve this problem. 

Alternatively, encourage students to use one of the many spaced repetition apps that are now readily available, such as Anki, Quizlet or Mathspace.

7 practical ideas for spaced repetition in the classroom

Implement the following 7 practical ideas to help take advantage of the spacing effect in the classroom.

1. Creating and organizing flashcards

This is particularly effective for language learning or subjects that require students to learn a lot of key terms.

First, help students to create accurate flashcards and teach them how to revise using the cards for active recall. Once this is in place, students can start engaging in independent learning using the Leitner system; moving cards into the next compartment once they can accurately recall all the information on them. To help students stay on track with this, dedicate one math homework every 1-2 weeks to testing themselves with their flashcards and moving the cards into the appropriate compartment.

2. Low-stakes quizzes

Use these at least once a week, or potentially in every lesson. They usually take five minutes to complete and a further five minutes to receive whole-class feedback.

A low-stakes quiz should not elicit any anxiety, which means there can be no consequence for getting a low score; students should understand that the purpose of the quiz is to improve learning.

Depending on the subject taught, a low-stakes quiz could be:

• A single question that requires a detailed response
• Five short-answer questions using mini whiteboards
• Spelling or times tables tests
• Writing out the definitions of keywords

It is an excellent way to revisit prior learning without taking too much time away from learning new content.

Exit tickets are an excellent low-stakes formative assessment to help teachers assess where students are in their learning. Explore Third Space Learning’s pre-made grade and math domain specific exit tickets to use regularly in your math lessons.

3. Lesson starters

This could be a short activity that students do as they come into the classroom and settle down. You could use this time to have students complete a low-stakes quiz or a short test.

Alternatively, ask students to spend five minutes completing a ‘brain dump’ – writing down everything they can remember about a previous topic. For older students, an appropriate lesson starter could be a single past paper question.

4. Homework exercises

This is an excellent way to incorporate spaced repetition without taking any time away from covering new content.

Ideally, dedicate at least half of any homework assignment to prior learning. This approach enables students to revisit two or three previous topics every week. It is a good reminder to students that reviewing previous learning is an important part of how to learn math.

5. Regular testing

If regular tests are part of your curriculum, include that week’s revision topics on the test, even if they are unrelated to the recently taught topics.

Students may find this a little uncomfortable to begin with, but it will encourage them to continually review previously learned material. It also reinforces that learning does not stop at the end of a lesson or a sequence of lessons; it is an ongoing process.

6. Interleaving

This is the process of combining two or more topics into a single question. Interleaving is a powerful teaching tool because it:

allows students to revisit previous topics alongside learning new content adds desirable difficulty to the task encourages learners to compare the two topics and identify the features of each one.

For example, 6th graders may practice fractions, decimals and percentages together rather than spending one week on each topic. Mixing problems on fractions, decimals, and percentages can help students identify which strategies to use for different problems. This helps embed these strategies in the long term memory and improve problem solving skills. 

Sample Problems:

1. Fractions: Simplify the fraction \frac{14}{28}
2. Decimals: Convert 0.25 to a fraction.
3. Percentages: What is 30% of 50?
4. Fractions: Add \frac{3}{5}+ \frac{2}{10} 
5. Decimals: Convert \frac{6}{9}​ to a decimal
6. Percentages: Express \frac{3}{4} as a percentage

By alternating between these different but related concepts, students get better at identifying which strategies to use for different types of problems, which improves overall problem-solving skills and retention.

7. Planning for spaced repetition in schemes of work

Without forward planning, it can be very difficult to revisit topics at regular intervals. Adapt schemes of work to include a reminder of which key topics to review each week. This ensures teachers revisit all topics at appropriate intervals.

Use any of the suggestions above for review. The most appropriate format depends on what else is taught that week, or whether there is a planned assessment.

Spaced repetition in math

Spaced repetition is extremely effective and easy to implement in mathematics lessons. Many topics build upon previous knowledge, making interleaving a popular form of spaced repetition.

Lesson starters and low-stakes quizzes can strategically reactivate relevant prior knowledge before introducing a new concept or math strategy.

Mathematics lessons constantly revisit mental math, and schemes of work often follow a spiral curriculum, revisiting and building on topics year after year.

Reactivating prior knowledge in a safe learning environment with Third Space Learning tutors: Adding decimals using the standard algorithm, 5th grade.

8 practical ideas for spaced repetition in math

Below are eight examples of how you could incorporate spaced repetition through interleaving into mathematics lessons:

1. Present lengths as fractions, surds or decimals when finding area and perimeter.
2. Use a mixture of cm and mm to interleave geometry questions with unit conversion.
3. Link finding the nth term with plotting the equation of a straight line.
4. Ask students to give their answers to percentage questions to multiple degrees of accuracy (e.g. 1 significant figure, 2 significant figures and 1 decimal place).
5. Calculate percentages and fractions from bar charts.
6. Describe time using fractions of an hour for students to convert into minutes.
7. Remind students of BODMAS when finding the area of a trapezium or substituting into algebraic expressions.
8. Give test scores as fractions to convert into a percentage.

Spaced repetition can have a significant impact on student learning and progress. It is also an effective way to revise for EOCs and other exams, avoiding cramming and the resulting stress and math anxiety.

However, it does require careful planning to successfully integrate it into classrooms and clear explanations and modeling from teachers to empower students to use it effectively during independent study sessions.

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The content in this article was originally written by secondary maths teacher, Zoe Benjamin, and has since been revised and adapted for US schools by elementary math teacher Christi Kulesza.