What is the optimal size of primary schools to improve learning in schools? Findings from Senegal.
Research on the economics of education has not reached a consensus on the role of school size on the learning process in schools. There are many analyses that look at class size but very few have focussed on school size in countries in Sub-Saharan Africa.
Extensive research (Kuziemko, 2006; Schwartz, Stiefel and Wiswall, 2011), predominantly conducted in developed countries, empirically shows that small schools offer a better learning environment. At the same time, proponents of schools with high pupil numbers (Conant, 1967; Callahan, 1962) build on the concept of economies of scale to justify their choice as to why a larger school is better. Other studies (e.g., Wyse, Keesler and Schneider, 2008) find no impact of school size on learning outcomes.
What can we learn about the ideal size of schools in Africa based on the causal analysis methods implemented to tackle the question in developed countries? A recent study, in the context of Senegal  provides some insights for developing countries.
The issue of school size in Africa
As part of the Fast Track  initiative, African countries implemented policies for mass enrolment, resulting in an impressive increase (of around 50%) in school enrolment rates. Teacher numbers have grown slightly less rapidly. Pupil-teacher ratios, particularly at pre-primary and primary school levels, remain high in Africa, as in many parts of the world.
Senegal has made progress in expanding access to education over the last decade. The number of primary school increased by 57.8% between 2002 and 2012, in part to achieve the Education for All objectives. However, studies have shown that as enrolment increased, quality has deteriorated (DeStefano et al., 2009).
To contain the growing rate of school enrolment, one of the major actions recommended by countries in the Sub-Saharan region, including Senegal, is to construct more schools. Should policy makers construct more schools and keep a low pupil/teacher ratio or allow schools to have an increased number of pupils? There are pedagogical issues to consider in both cases.
Data and analyses
To answer this question, data collected by the World Bank, and the Senegalese Ministry of Education as part of an assessment on the impact of school projects was examined. Data on student learning has been collected from over 500 schools located across Senegal. Contextual information has also been collected. Doubly robust regression models have been developed to estimate the effect of school size on student performance in French and mathematics and to gauge the optimal number of students for primary schools in Senegal.
The analyses show that school size has no effect on student performance at the start of the learning process (second grade). However, by the fourth grade, in schools with many students, adverse effects on student performance can be observed, both in French and in mathematics, and both in the medium and long term. This difference between 2nd and 4th grade students can be explained by the fact that fourth graders have spent more time in the education system whereas, at the start of the learning process, schools have not yet left their mark on young learners, who demonstrate learning more in relation to family characteristics.
These general results have been supplemented by heterogeneity analyses of the effects of school size. Heterogeneity analyses show that there are effects of school size on all pupils, regardless of their performance level, and that they are more visible among girls and in urban locations (where schools are particularly large).
Schools that are neither too big nor too small
A large number of sensitivity analyses have been conducted to assess the variability of the results of the analysis according to seven different scenarios. These have shown that schools with large numbers of pupils are equally harmful to educational attainment as schools that are too small. Middle-sized schools appear to be a good choice. Based on this research, the ideal numbers for a primary school in Senegal would be in the range of 470 to 500 pupils.
To respond effectively to the quality-quantity debate, it would be helpful to examine the question in other African countries. This would help education planners in their work as they seek to optimize learning conditions in schools.
Callahan, R. E. 1962. Education and the cult of efficiency: A study of the social forces that have shaped the administration of the public schools. Chicago: University of Chicago Press.
Conant, J. B. 1967. The comprehensive high school. New York: McGraw-Hill.
Destefano, J., Lynd, M.R. et Thornton, B. 2009. La qualité de l’éducation de base au Sénégal : une revue. Rapport final prepared for USAID Senegal. Consulté en november 2012
Kuziemko, I. 2006. “Using shocks to school enrollment to estimate the effect of school size on student achievement”. Dans : Economics of Education Review, Vol. 25, N°. 1, p. 63-75.
Schwartz, A. E.; Stiefel, L. ; Wiswall, M. 2011. “Do small schools improve performance in large, urban districts? Causal evidence from New York City”. Document de travail N°. 04-11.Consulté en septembre 2013
Wyse, E., Keesler, V. ; Schneider, B. 2008. “Assessing the effect of small school size on mathematics achievement: a score matching approach". Teachers College Record, Vol. 110, N°9, pp. 1879-1900.
 see Chapter 2: Estimating the Causal Effect of School Size on Educational Attainment p. 40.
 The Fast Track initiative became the Global Partnership for Education on 21 September 2011.