We might associate ‘top schools’ with having the lion's share of academic high-achievers. However, when we look at the distribution of achievement across all students within schools and compare it to average differences between schools, the story is not so straightforward.
3 male students happily conducting a science experiment wearing lab cots and goggles.

Part 2: Examining NAPLAN data 2013 to 2019 

We might associate ‘top schools’ with having the lion's share of academic high-achievers. However, when we look at the distribution of achievement across all students within schools and compare it to average differences between schools, the story is not so straightforward.  

In an analysis of National Assessment Program – Literacy and Numeracy (NAPLAN) data from 2013 to 2019, we found that the gaps between the highest- and lowest-achieving students within schools are bigger than the gaps between the average scores of the highest- and lowest-achieving schools. In other words, most of the variation in students’ literacy and numeracy scores is explained by differences between individual students, not the school they attend.

What we learnt

Figure 1 shows this effect graphically. In a randomly selected subset of schools, we plotted literacy achievement scores for each individual student (vertical axis) grouped by the school they attend (horizontal axis) and ranked schools by their average. The spread of individual scores across schools overlaps considerably, despite schools having different averages. This shows that a larger proportion of the variation in literacy is due to differences between the students themselves.  

Even though schools with high average achievement have more high-achieving students and fewer poor-achieving students, most schools have a range of students across the achievement distribution. 

The same interpretation can be applied to the results for the numeracy tests (see Figure 2).  

Figure 1: Distribution of Year 3 NAPLAN reading scores for students within schools

Note: Dark blue dots indicate school mean score. Random sample of 200 schools.

Differences between schools are smaller in primary school (Years 3 and 5), compared with secondary school (Years 7 and 9). This may be seen as reassuring: where the differences between schools are lower, the potential problem of ‘residualisation’ is less of a concern (that is, high clustering of lower performing students in some schools presenting additional challenges of turning schools around).

Figures 2 and 3 show how much of the variance in students’ literacy and numeracy scores is captured by average differences between schools, and how much is related to differences between individuals, regardless of school.

For primary school year levels, 25–28% of the variance in literacy achievement is captured by between-school differences. The remaining 72–75% of the variance is explained by differences between individual students. For secondary school year levels, between-school differences increase to 36–37%.

Figure 2: What explains variance in literacy outcomes

Figure 3: What explains variance in numeracy outcomes

Why this matters

These results reveal that there is no ‘average school’ with ‘average students.’ In nearly every school there are above-average performers and students who need more support. Figure 1 shows this graphically: even in high-average schools, some students obtain low NAPLAN scores. These students can’t be forgotten and high-average schools should ensure they have strategies in place to provide targeted support.

On the other hand, some schools have a larger share of students with below-average achievement than other schools. Identifying these schools and working with them to implement school-wide strategies for literacy and numeracy support could benefit all their students.  

The fact that between-student differences explain most of the variation in student achievement also affirms the potential influence non-school factors can play on student learning. Studies have shown that parental aspiration and support provided at home to students are two contributing factors to student success in learning.

Overall, between-school differences explain less of the variance in student outcomes in literacy and numeracy in the primary school grades compared with secondary school grades. Fewer between-school differences in the primary years indicate that school segregation is not endemic in Australia and has the potential to change. However, larger achievement differences between schools in Year 7 and 9 suggest that students are more likely to be grouped with other students like themselves in secondary schools. This phenomenon has the potential to widen the gaps between high- and low-achieving secondary schools.

Next steps

Regardless of the differences between schools, and the differences between students within schools, all students need access to high-quality instruction that will support them to achieve. Schools and teachers need to be adequately equipped to support excellent and equitable outcomes for all students.

AERO is working towards providing high-quality resources for teachers in all Australian schools to help teachers implement practices shown to support learning for students across the spectrum of achievement.

This is the second of a series of insights on educational excellence and equity. This work is based on AERO's analysis of NAPLAN data.