Small class size has at best a small effect on academic achievement

Reducing class size is often suggested as a way of improving pupil performance. However evidence from a new Campbell systematic review suggests that reducing class size has at best only a very small effect.

The review summarises findings from relevant studies that measured the effects of class size on academic achievement. A total of 127 studies were analysed, including 45 studies that used data from the US Student Teacher Achievement Ratio (STAR) programme that reduced class sizes substantially in kindergarten to grade 3 (Years 1 to Year 4). However only ten studies, including four of the STAR programme, could be included in the meta-analysis.

Their analysis focused on effects on maths and reading and found a small positive effect of reducing class size on pupils’ reading achievement and a negative, but statistically insignificant, effect on maths. For reading, the weighted average effect size was +0.11, and the weighted average effect size for maths was -0.03.

For the four studies using data from the STAR programme, the researchers found a positive effect of smaller class sizes for both reading and maths. However, the average effect sizes were still very small and do not change the overall finding.

Source: Small class sizes for improving student achievement in primary and secondary schools: a systematic review (October 2018), Campbell Systematic Reviews 2018:10

The impact of more teachers and smaller classes in the early years

What difference do smaller class sizes, and more teachers, make in early childhood education (ECE)?

A meta-analysis by Jocelyn Bowne and colleagues, published in Educational Evaluation and Policy Analysis, attempts to find some answers. The analysis included evaluations of ECE programs in the US between 1960 and 2007. The evaluations were either experimental studies, used a high-quality quasi-experimental design, or showed baseline equivalence of treatment and control participants. In total, 38 studies were included, all of which looked at children ages 3 to 5 years old attending an ECE center for 10 hours a week or more for at least 4 months. Child-teacher ratios ranged from 5:1 to 15:1 and class sizes from 11 to 25.

The findings were as follows:

  • Above a child–teacher ratio of 7.5:1, changing the ratio had no effect on children’s cognitive and achievement outcomes. Below this, a reduction of the ratio by one child per teacher predicted an effect size of +0.22.
  • For class sizes greater than 15, increasing the size of the class had little effect on children’s cognitive and achievement outcomes. Below this, one child fewer in the class size predicted an effect size of +0.10.

The authors caution that these findings are correlational, rather than causal, so changing class sizes or ratios, certainly at scale, may not lead to these results. However, they conclude that “very small and/or well-staffed classrooms might confer some small benefits for children’s cognitive and academic learning”.

Source: A meta-analysis of class sizes and ratios in early childhood education programs: Are thresholds of quality associated with greater impacts on cognitive, achievement, and socioemotional outcomes? (February 2017), Educational Evaluation and Policy Analysis, Vol 39, Issue 3

How parents respond to increased class size

A new working paper from the Swedish Ministry of Employment explores the responses of parents to variations in class size caused by a maximum class size rule in Swedish schools. This includes analysis by parental income.

The authors found that in response to an increase in class size: (1) only high-income parents helped their children more with homework; (2) all parents were more likely to move their child to another school; and (3) only low-income children found their teachers harder to follow when taught in a larger class.

Data for the study was taken from the Evaluation Through Follow-up (ETF) project, run by Göteborg University. This contains measures of pupil performance in the final year of upper primary school for roughly a 10% sample of the cohorts born in 1967, 1972, and 1982, and a 5% sample for the cohort born in 1977. The project included questionnaires distributed when pupils were 13 with information about the behaviour of parents, children, and teachers. In addition, data on parental income and education was taken from the Income Tax Register and the Educational Register.

The authors suggest that their findings help explain why the negative effect of class size on achievement is greater among low-income pupils.

Source: Parental Responses to Public Investments in Children: Evidence from a Maximum Class Size Rule (2015), Institute for Evaluation of Labour Market and Education Policy.

Primary school size matters for some children

A new article in Educational Evaluation and Policy Analysis looks at primary school size and academic performance, and concludes that for most pupils there is no causal relationship.

The authors used administrative records on 691,450 pupils aged 8-11 who attended 1,417 schools in North Carolina between 2004 and 2010. The data contained end-of-year maths and reading scores, pupil demographics, classroom identifiers, and a set of school-level characteristics including total enrolment, average daily attendance, suspensions, expulsions, crimes per 1,000 pupils, and geographic locale.

The primary analysis provided no evidence of a causal relationship between school size and overall pupil achievement, regardless of whether school size was measured at the school or year level.

However, two subgroups were significantly harmed by increases in school size. The maths and reading achievement of pupils with special educational needs (SEN) was lower in large schools, as was the reading (but not maths) achievement of socio-economically disadvantaged pupils. The authors suggest that SEN pupils may be particularly sensitive to increases in school size either because larger schools are less able to match their needs to relevant support programmes, or because they are more sensitive to the weaker social bonds that may be inherent in larger schools. The authors also cite previous research that suggests that disadvantaged pupils who receive less attention at home may benefit from the greater individual attention provided by smaller schools.

Source: The Effect of Primary School Size on Academic Achievement (2015), Educational Evaluation and Policy Analysis, 37(1).

Should we be trying to reduce class sizes?

Class size is a hot topic again. A predicted population increase and funding decrease, mean that pressure on class sizes is likely to grow. A research review from the Department for Education considers a number of issues around class size in England, including the impact on educational outcomes. The authors found a number of benefits from smaller classes, such as individual pupils being the focus of the teacher’s attention for longer.

However, previous research has shown that reducing class size is beneficial when classes are small, around 15 pupils. With budgets stretched, schools should consider the financial benefits of allowing classes to grow slightly. This may allow them to preserve resources for more effective ways of improving attainment, such as increasing teacher effectiveness.

Source: Class size and education in England evidence report (2011), Department for Education