PISA 2006: School context of science achievement: How ready are our 15-year-olds for tomorrow's world?

School demographic characteristics and decile

This chapter aims to examine the relationship between the demographic make-up of schools (that is, location, school size, and class size), their decile ranking, and student achievement. Previous international studies (for example, the Progress in International Reading Literacy Study, Caygill & Chamberlain 2004; Trends in International Mathematics and Science Study, Chamberlain & Caygill 2002; and PISA 2000, Sturrock & May 2002) have shown that school demographics influence student achievement in some respects. In these studies, students enrolled in larger schools and high decile schools (often large schools are high decile) performed higher on average than other students. One of the challenges New Zealand faces is how to reconcile these differences so that the learning needs of each student are met.

Demographic characteristics

The location and size of a school, as well as the size of classes and the economic composition of the student population within the school, may require variations to be made in the school’s organisation or curriculum to meet the needs of the students adequately. The results of analyses of these variables are presented in this section.

Location of school

Students in schools in rural locations can potentially have quite different needs to students in schools in urban locations. PISA categorises the location of schools under five headings: rural, small town, town, city, and large city. There are some differences in achievement among New Zealand 15-year-old students between those in the smaller areas (rural and small town) and those in cities. Generally, students in schools in the larger locations had higher science achievement, on average, than those in smaller locations.

Figure 1: Mean science achievement of New Zealand students, by location of school

Notes:

Standard errors are presented in parentheses. Points indicate best estimates of the achievement of 15-year-old students in the population, while lines extending from the points indicate the 95% confidence interval – the region in which the population mean is most likely to lie.

Size of school

The size of a school can potentially have an impact on the education of its students, with economies of scale possible with larger schools, but a sense of intimacy and knowledge of the needs of students potentially easier with smaller schools. The New Zealand schools involved in PISA were divided into four broad bands of school size, as illustrated in Table 1. Students in the larger schools (more than 1,200) had higher scientific literacy achievement than students in the smaller schools. Note that this analysis does not show a causal relationship – a bigger school does not necessarily guarantee higher achievement. Further analyses that include other factors are required to explain this result.

Table 1: Mean science achievement of New Zealand students, by school size band

Note:

(s.e.) standard errors are presented in parentheses.

Class sizes

Research has shown that smaller classes can have a positive effect on the learning of students, although there appear to be more benefits for younger children (Podmore, 1999). Principals were asked about the number of students in the average English class in Year 11 (other countries had similar appropriate categories of language-of-the-test and year level). This question was intended as a proxy for general student-teacher ratios.

In New Zealand, most of the students were in classes of size 26 to 30 (54%) or 21 to 25 (31%). In comparison, Australia and the United Kingdom had more students in the smaller class size of 21 to 25 (46% and 45% respectively) and fewer students in the larger class size of 26 to 30 (44% each). Interestingly, the majority of students in Finland were in classes of size 25 or lower (46% in classes of 16 to 20 and 48% in classes of 21 to 25), while the majority of students in Hong Kong-China were in classes of 36 or more (58% in classes of 36 to 40 and 26% in classes of 41 to 45).

Table 2: Proportion of students in each class size band

Notes:

5% of students had missing data for this question in New Zealand, compared with 2% on average across the OECD.

In large-scale snapshot studies such as PISA, examining the relationship between class size and achievement is often confounded by the fact that smaller class sizes are often used for students needing remedial help. In addition, the high-performing countries included both those with more students in smaller classes (Finland) and those with more students in larger classes (Hong Kong-China) than New Zealand.

Decile

The decile indicator of a school relates to the extent to which a school draws its students from low socio-economic communities. Five factors are used to calculate decile: household income, occupation, household crowding, educational qualifications, and the income support levels of houses in the areas a school draws its students from. Schools are ranked and then divided into 10 groups, called deciles.

As shown in Figure 2, the achievement of New Zealand 15-year-old students increased with the increasing socio-economic grouping of the school, although differences between adjacent deciles are not always significant (for example, deciles 2 and 3 are approximately the same). That is, in general, students in schools where the household income, occupation, and educational qualifications in the area were high and the household crowding and income support levels were low had higher achievement than those in lower socio-economic areas.

Figure 2: Mean science achievement of New Zealand students, by decile grouping

Notes:

Standard errors are given in parentheses. Points indicate best estimates of the achievement of 15-year-old students in the population, while lines extending from the points indicate the 95% confidence interval – the region in which the population mean is most likely to lie.

‘Ind’ stands for ‘independent schools’. Although some of these have decile ratings, this is not consistent across all independent schools.

Along with mean achievement, PISA also provides the opportunity to look at the higher and lower performers using proficiency levels. Six scientific proficiency levels link student achievement scores to the types of tasks that students at each level would typically be expected to perform. At the highest level, level 6, students can typically perform tasks involving complex thinking and analysis, as well as easier tasks at the lower levels. Students at level 1 demonstrate much more limited scientific knowledge and can only apply it in familiar situations.

The proportions of students at each of the proficiency levels can not be examined for individual deciles because the number of students at each level is too small. To overcome this problem, the deciles are grouped into quintiles; that is, decile 1 with 2, decile 3 with 4, etc. as shown in Figure 3. As might be expected from an examination of the means for individual groupings, larger proportions of students in independent, deciles 9 to 10, and deciles 7 to 8 schools performed at the higher proficiency levels. Similarly, fewer students in these decile groupings performed at the lower proficiency levels.

Figure 3 also shows that there are very high-performing students in all decile bands as well as students who performed at lower levels of proficiency.

Figure 3: Scientific literacy proficiency levels of New Zealand students, by decile grouping