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The shady sides of smaller class sizes

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“Education is our passport to the future, for tomorrow belongs to the people who prepare for it today.” What the pugnacious Malcom X expressed in 1964, is nowadays – at least in its principles – a consensus view in the worlds of science, politics and business. However, while the great importance of education for the individual as well as for the overall societal development is broadly accepted, the (potential) influence of different education policies has to be scrutinized even more critically.

In the last decades, educational debates were often dominated by calls for class size regulation policies. Since smaller classes usually enable higher personal attention for students, such demands seem to be obvious. Despite the mentioned benefit, a holistic evaluation raises the question if class size reductions are really as worthwhile as widely believed? As Harris/Plank (2001) and Jepsen/Rivkin (2009) show based on the cases of class size reduction programs in the US states of Michigan and California, there might be a tradeoff between the average teacher quality and class size. On the one hand, class size reduction programs lead to the necessity of hiring a large number of teachers, even if this means bringing less qualified personal into the job, given the available application pool. On the other hand, such programs are very cost-intensive due to the requirement for additional teachers, classrooms and equipment. Together with the traditionally tight education budget, this leads to deficits with regard to sufficient teacher salaries as well as to the financing of teacher training.

In light of the opportunity costs principle and since the aspects mentioned above tend to affect the average teacher quality in a negative way, we somehow have to weigh the benefits of smaller classes against those of better teachers. Fortunately, Hattie (2009) with his unprecedented extensive empirical study is providing a terrific tool for doing this. By synthesizing more than 800 meta-analyses about the influences of a total number of 138 different programs, innovations and policies on the student achievement, he is able to determine an effect size for all of them. While a value of 0.21 indicates that the class size has only a small positive influence on student achievement, different teacher quality related issues like teacher clarity, teacher-student relationship or professional development have effect sizes above 0.60 and are among the most influential effects. Does this mean that we should not care about class size at all? As the small but still positive effect size shows, this is clearly not the case. Nevertheless, in consideration of (opportunity) costs focusing on measures to improve the average teacher quality might be more beneficial. Since such improvements cannot be achieved from one day to the next, these medium-term development programs should be supplemented by short-term measures like assigning disproportionally large classes to the best teachers (Hansen (2013)).

Tim Silberberger


Hansen, Michael (2013): Right-sizing the Classroom: Making the Most of Great Teachers; Thomas Fordham Institute.

Harris, Douglas and David N. Plank (2001): Does Class Size Reduction Come at the Expense of Teacher Quality?; Policy Report Number 4 (November 2001); The Education Policy Center at Michigan State University.

Hattie, John (2009): Visible learning. A synthesis of over 800 meta-analyses relating to achievement; London.

Jepsen, Christopher and Steven Rivkin (2009): Class Size Reduction and Student Achievement: The Potential Tradeoff between Teacher Quality and Class Size; Journal of Human Resources, 44:1 (2009) 223-250.


Author: studentnovasbe

Master student in Nova Sbe

One thought on “The shady sides of smaller class sizes

  1. The importance of the class size on children achievements has been extensively discussed. Some studies as you mention conclude that the reduction of the class size have a positive effect on the students’ performance and knowledge. However there are literatures that do not support these results and argue that there may be other factors that cause the students to improve their performance besides the decrease in the number of students. As mentioned the reduction in the class size is very costly for the government. For this reason, I believe it is important to accurately identify the most efficient policy for the government to invest.