How has the introduction of department-wide interleaving affected students’ rates of learning?
Two years ago we took the decision to introduce department-wide interleaving (and spaced practice) through the introduction of Numeracy Ninjas, weekly skill quizzes (on a mixture of topics) and delayed end-of-unit testing. This was in response to our learning about Desirable Difficulties and the impact university laboratory studies had shown these can have on learning. For more information about Desirable Difficulties, read a summary here.
Previously, our department typically delivered blocked practice teaching from the start of year 7 until Xmas in year 11. We then switched to interleaved practice, giving students a weekly practice GCSE exam paper and feeding back on their performance in class, modeling solutions etc. Approximately 3 times per year we gave all students in KS4 a summative assessment which was a full previous GCSE exam paper and recorded their A*-G grade performance against the real grade boundaries for that paper. For the 2013-14 cohort we plotted their progress flight path across KS4 as shown below:
In those days, ‘minimum expected progress’ was the important currency and thus the vertical axis shows how many GCSE grades the mean average student needed to progress to achieve their minimum expected progress GCSE grade (remember 3LOP?!). The important point is that units on the vertical axis are in whole GCSE grades (A, B, C etc).
What struck us was how little retained-progress students made for 2.3 years on the course whilst they were studying using almost exclusively blocked practice methods, approximately 0.5 GCSE grades. We were teaching them a skill, they were reproducing it in their books, but they could not retain and apply it on a delayed assessment. Once they switched to interleaved practice their rate of progress greatly increased, approximately 1.4 GCSE grade over 0.7 years.
The flight path highlighted how critical students fully engaging with the practice papers was in the final few months of the GCSE course. This was a time when they were being pulled in many different directions as they had to balance their intense and peaking workload across their GCSE subjects.
Naturally, the flight path led to the question being raised, “what if we brought the interleaving forward to earlier in the course? Would their rate of progress through years 9 and 10 increase so by the time they reached year 11 it was either more secure, and/or would lead to greater final attainment?” Relatively speaking, we thought the potential benefits significantly outweighed the consequences if it was ineffective and so introduced interleaving across the department’s practice through Numeracy Ninjas in year 7, MathsBox Weekly Skill Checks in years 8 to 11 and delayed (3 week after finish teaching) end-of-unit testing in all year groups. These 3 initiatives ensured that students would be getting interleaved practice right the way through their 5 years with us, rather than just in the final 7 months.
This year we sat all year groups on exactly the same assessments during each term which allowed us to plot a flight path across the 5 years under the assumption that each year group is of similar ability; this is fairly reasonable, looking at prior attainment. We used the Edexcel Practice Set papers which were created by combining questions from previous GCSE papers. The benefit of this was that they came with national performance data (ResultsPlus) for each question and so we were able to back-calculate A*-G grade boundaries for each paper and put them onto the 9-1 scale by using the grade 1-G, 4-C, 7-A equivalencies.
Now that we’ve been delivering interleaving at a department-wide level for 2 years, what impact has it made on students’ rates of progress?
The first thing to note is that the two flight paths cannot be compared on the same axes. There are more 9-1 grades that A*-G grades and thus you can’t do a 121 mapping onto similar axes. Nonetheless, the differences in shape between the flight paths is striking. Since the introduction of interleaving the flight path has changed from a hockey-stick to almost perfectly linear.
Even though the ‘width’ of 9-1 grades are narrower than A*-G grades, the rate of progress in years 9 and 10, even with a conservative estimate is at least twice, if not more, than it was before.
Students are retaining what we are teaching them and able to apply it on assessments cumulatively through the course much better than previously. There is now much less pressure for students to make the rapid progress gains in the final few months of year 11.
Of course, what ecological validity brings, unavoidable confounding variables undermine… I certainly believe however that the changes to introducing interleaving throughout the course and department wide are the most siginificant changes, by far, that we have made between these data sets which could explain the differences in shapes (and gradients) of progress flight paths.
This adds further weight to recent studies in real-world maths classrooms of the learning benefits of interleaving and suggests that simple free and commercially available resources such and Numeracy Ninjas, MathsBox Weekly Skill Checks and Edexcel End-of-Unit Tests are enough to fascilitate these benefits.