If we want to learn something that sticks, we know that repetition is important. It has been established many times that spaced practice works better than cramming everything at once. This is called the spacing effect, and while it sounds very logical in theory, recent research shows that practice can sometimes be stubborn—especially when the research is done in a real classroom environment with real students.

In a recent study at the University of Kassel, Krauspe and colleagues investigated whether adding worked examples to spaced practice sessions in primary education would help math stick better. Students around 10 years old were given an explanation of multiplication and then allowed to practice. Some students were given all the practice problems at once (mass practice), while others were given exercises spread out over several days (spacing). At the same time, some students practised only with problems they had to solve themselves, while others received additional support through worked examples that they had to explain to themselves.

What is special about this study is that it was conducted entirely in real classrooms, with students and teachers following their daily school routines. This sets this study apart from previous experiments that often occur under controlled, possibly less realistic, laboratory conditions.

The expectation was that students who practised in a spaced manner and with worked-out examples would score best in the long term. But what turned out? Surprisingly, there was no clear difference eight weeks after the lessons and exercises. Students remembered the material just as well (or poorly), regardless of whether they had practised in a spaced manner, had used worked-out examples, or both.

Reporting such null results is essential because they also tell us a lot about what does and does not work in practice. Also, don’t forget: one study alone is never enough to draw definitive conclusions. So don’t think that spaced repetition and elaborated don’t work; on the contrary, there is more research that it does.

Why, then, did these approaches not work as expected? Perhaps worked examples work better during the instructional phase, or the distribution of exercises needs to be planned differently. Maybe the complexity of the subject matter also plays a role. These are all questions for further research.

For now, this study mainly shows that there are no magic formulas in educational practice, and you know again why I always talk about ‘can work’ instead of ‘what works’ in education. Real learning comes from careful weighing, trying out, and adjusting in the context of real classroom life.

Abstract of the study :

Background
The acquisition of lasting knowledge that is accessible for a long time is an important educational goal. Spacing the learning or practice phase across multiple sessions fosters lasting learning, but the effect is less robust for complex material.
Aims
We examined whether the meaningful elaboration of the learning material, evoked by means of self-explaining worked examples, contributes to a more robust spacing effect concerning the lasting learning in mathematics.
Sample
Participants were fourth graders (N = 213).
Methods
Children received a formal instruction to long multiplication in school. Thereafter, they practiced the procedure either in a massed or a spaced manner, and either by pure problem solving or by additionally self-explaining worked examples in their regular math lessons. Time on task was hero constant in all conditions. In a delayed test after eight weeks, children’s procedural and conceptual knowledge was assessed. Their general math ability and their specific prior knowledge served as control variables.
Results
Contrary to our expectations, there was neither a main effect of worked examples nor of spacing, and no interaction emerged between the two variables. Exploratory analyzes revealed the same results concerning the forgetting rate between the last practice set and the test. These null effects were confirmed by Bayesian analyses. Only children’s general math ability and their prior knowledge predicted their test performance.
Conclusions
The results suggest that the spacing effect in mathematics does not emerge reliably, even not when stimulated by worked examples. Further research on potential boundary conditions is required.