At Datalab we write about half a dozen blogposts in a typical month. Some we slave over and others we knock out in a matter of minutes, usually with one eye on the football or Paw Patrol. Being unashamed data wonks, we then pore over Google Analytics to see which of our posts have left the biggest impression. We are often miffed by how this seems to be inversely correlated with the effort we put in.

Earlier in the week we had a lot of positive feedback on Twitter for the chart below, which we had lying around as a by-product of some other work we had been doing. So we thought we would write it up for posterity.

The chart shows the percentage of pupils in the 2016 Key Stage 4 cohort (state-funded mainstream schools only) who achieved the expected standard at Key Stage 1, Key Stage 2 and Key Stage 4 by month of birth. We only included pupils who were assessed at all three Key Stages. The indicators used were:

  • % achieving Level 2B or above in reading, writing and maths at Key Stage 1
  • % achieving Level 4B or above in reading, writing and maths at Key Stage 2
  • % achieving five or more GCSEs at grades A*-C (or equivalent) including English and maths at Key Stage 4

As luck would have it, the averages of these three indicators are broadly similar for pupils we are looking at, at 56%, 58% and 59% respectively.

% achieving expected standard by month of birth and key stage, 2016 KS4 cohort

The chart shows that August-born pupils close the gap as they get older but remain behind September-born peers by the end of KS4. However, colleagues at the Institute for Fiscal Studies have previously found no evidence of long-term differences in outcomes among adults [PDF].

The average Progress 8 score for August-born pupils is 0.18 grades per subject higher than September-born pupils indicating (as the chart above suggests) that they close the gap slightly between Key Stage 2 and Key Stage 4. However, in terms of raw attainment (Attainment 8), they remain 0.3 grades per subject behind. On average, September-born pupils achieved 52.4 points compared to 49.5 among August-born pupils.

The cohort used in the chart above completed Key Stage 2 in the days of Levels. To bring things more up-to-date, in the following chart we look at the cohort which completed Key Stage 2 in 2016, when scaled scores had come into effect. As the expected standard at Key Stage 2 is higher, we have redefined the Key Stage 1 standard and include the Foundation Stage:

  • % achieving a good level of development in the Foundation Stage
  • % achieving Level 2B or above in reading, writing and maths (with at least one Level 2A or above) at Key Stage 1
  • % achieving the expected standard or above in reading, writing and maths at Key Stage 2

Although we don’t have data on achievement in Year 4, we have included it so that each series is two years apart and we have taken a punt on what we think the results would show for September-born and August-born pupils if we did have it.

% achieving expected standard by month of birth and key stage, 2016 KS2 cohort

Though crude, the chart suggests that the rate of catch-up for August born pupils was slightly quicker between Key Stage 1 and Key Stage 2 than between Foundation Stage and Key Stage 1.

The upshot

What is the upshot of all of this?

Most secondary schools are large enough not to suffer too much from year-on-year changes in the age profile of its cohorts.

But most primary schools are not.

Performance can be affected by an increased proportion of summer-born pupils (primary school performance is somewhat volatile in any event).

(For those who use FFT Aspire, age is one of the pupil characteristics used in contextual value added progress measures. Term of birth is also to be added shortly to the self-evaluation part of Aspire.)

We have long argued that age, gender and other contextual factors should be considered when evaluating a school’s performance.

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