I once taught a Year 7 top set and a Year 10 bottom set in consecutive lessons on a Friday afternoon. The proximity of the two classes got me thinking about their relative attainment and progress. Suppose I accidentally mixed up my lessons. Would the Year 10s have found the Year-7 lesson easy? Would the Year 7s have struggled with the Year-10 lesson? What if I’d given both classes the same assessment? Would the Year 10s invariably have done better than the Year 7s? At the end of the year, I wondered how much of each class’s improvement was the result of the efforts of my fellow teachers and I - and how much was the result of family background or general maturation.

A new paper from researchers in the UK and the Netherlands addresses some of these questions. The researchers found that younger pupils tend to make more progress. When you compare Year 2 pupils with those in Year 1, there is a big difference of more than one effect size in reading and maths. When you compare Year 6 pupils with those in Year 5, the improvement is still substantial, but the effect size has shrunk to 0.5. The effect size measures the difference between groups. A useful comparison is that an effect size of 0.5 is the difference between the average height of 14-year-old and 18-year-old girls.

In practice, this means that if you were to compare the work of an average Year 1 pupil and an average Year 2 pupil, it would be fairly obvious which pupil was in which year. But if you were to do the same with pupils in Years 5 and 6, it would be less obvious. This study focuses only on primary pupils, but the authors note that other research shows learning gains keep declining in secondary.

Finding ‘huge gains’ in pupil progress

These researchers have also come up with a clever way to investigate if these improvements are caused by schooling. It would be unethical to set up a “non-schooled” control group, so instead they compared the performance of the very oldest children in one year group and the very youngest in the year above. These pupils were essentially the same age, but owing to the cut-offs for entry into school, some of them had an extra year of school. Using this method, the researchers calculated that about 40 per cent of the improvement in reading and maths was because of the effects of schooling.

What are the implications of this research? It certainly reinforces the importance of primary education, given the huge gains that are made at this age. It also suggests that we might want to evaluate educational programmes differently depending on the age of the pupils. An effect size of 0.2 might not be much in Year 3, but it is a lot in Year 10.

One interesting area of further study involves the progress made in different subjects. As the researchers note, in the later years of education there is more of a focus on applying literacy and numeracy skills in subjects such as history, geography and science. To return to my original musings about the difference between Years 7 and 10: at secondary, high-attaining pupils in younger year groups will often be doing better than lower-attaining pupils in older year groups.

Daisy Christodoulou is director of education at No More Marking and the author of Making Good Progress? and Seven Myths about Education. She tweets @daisychristo

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