Some research

Class size cannot be considered in isolation from other factors

John Hattie and class size

John Hattie's book Visible Learnings gives class size a small effect size on student achievement, however Invisible Learnings? A commentary on John Hattie's 'Visible Learning: A synthesis of over 800 meta-analyses relating to achievement' written by Massey university academics Ivan Snook, John Clark, Richard Harker, Anne-Marie O'Neill and John O'Neill looks at Hattie's findings on class size and expresses concern at the validity of these.

"Hattie has been cited as finding "that class size is not important and this has excited the attention of those concerned about financing of schools, who conclude they can economise on class size," it reads. These results however fail to look at contributing factors such as professional development and the ability for teachers to spend more time with students.

"Hattie recognises that 'class size' cannot usefully be considered in isolation from other potentially important, pedagogically related variables. Reducing class size may have only a small effect when considered in isolation but that's not the issue. What matters is that reducing class size permits the teacher (and children) to do things differently.


weblink Read Invisible learnings - available from school and local public libraries

Blatchford, Bassett and Brown study

Blatchford, Bassett and Brown (2011) studied the effects of actual class size on student engagement and student-teacher relationships. The interactions of students at different levels in classes of different sizes were systematically recorded and analysed.

weblink Examining the effects of class size on classroom engagement and teacher-pupil interaction: Differences in relation to pupils prior attainment and primary vs. secondary schools. Blatchford, Bassett and Brown. 2011

Key results of the study indicated:

  • At both primary and secondary level smaller classes correlated with more individual attention to students by the teachers. At the secondary level an increase of five students per class resulted in the chance of a pupil being the focus of a teacher's attention decreasing by about a quarter.
  • At both primary and secondary level smaller classes correlated with more active interaction between students and teachers.
  • At both primary and secondary level smaller classes correlated with increased classroom engagement, which was most marked for lower attaining students. For lower ability secondary students an increase of five students in class size was associated with on task behaviour decreasing by about one quarter, a larger difference than for low achieving students in primary.
  • Pupils tend to interact more with each other, both on and off task, as pupil number per class increases.
  • As secondary class size increases the amount of teacher-centric activity increased.
  • For low attaining students there is some evidence of teachers having to deal with more negative behaviour as class size increases.
  • There is no threshold above or below which effects are most evident.

Main implications of study:
The effects of small class sizes extends into secondary and does not tail off. In particular, the classroom engagement effects for lower attainment students are more marked in secondary.

Smaller classes can benefit all students, but lower attaining students can benefit from smaller classes at secondary level through more individual attention and facilitation of engagement in learning.

Small classes can allow teachers to engage in more individualized teaching and can be used as part of more differentiation in curriculum.

The negative impact of adding students to classes are cumulative, and the positive impact of reducing the number of students is cumulative with respect to individual attention and facilitation of engagement in learning.

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Last modified on Monday, 12 December 2016 09:27