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Optimized school catchment zones for French-speaking Switzerland and Quebec

The Swiss study on social mixing in urban schools that we conducted at the Center for Democracy Studies Aarau (ZDA) is now available in English and French. It contains analyses of the cities of Geneva and Lausanne, where the algorithm developed at the ZDA reveals an untapped potential for a better social and ethnic mix in schools and thus for greater equality of opportunity. The algorithm, which is the only one of its kind at the international level, is now also integrated into a large-scale reform plan developed by the civic organisation École ensemble for the Canadian province of Quebec.

The Swiss study

A successful school career and good career prospects depend – at least in part – on the school attended. This situation jeopardizes equal opportunities, especially for students from neighborhoods with a high proportion of migrant and socially weaker families. In order to create equal opportunities, schools must be more mixed.

This study examined the assignment of children to lower-level primary schools, using the cities of Basel, Bern, Geneva, Lausanne, Winterthur and Zurich as examples. At the same time, it examined what changes would be needed in the boundaries of the catchment areas to achieve a better social and ethnic mix. To support school allocation and school space planning in this respect, the authors of the study developed an optimization algorithm.

The algorithm – a data-driven method for optimizing school catchment areas
In Switzerland, an initial approximate distribution of students is based on catchment areas. These catchment areas are adjusted each year to ensure balanced class populations. The data-based procedure proposes adjustments in border areas that, in addition to balancing class populations and short and safe school routes, also aim to level out the composition of schools. To this end, a “concentration index” is calculated for all schools and street blocks on the proportion of students speaking foreign languages and having parents with low educational attainment. Then, an intuitively understandable procedure is used to search for the favorable exchange of street blocks in the border area between schools.

Specific results for Geneva and Lausanne

  • The relevant authorities in Geneva and Lausanne were not willing to provide information on the current distribution of schools, and in the case of Geneva, access to public education statistics data was not granted in order to make provisional assessments of the current catchment areas.
  • For the Geneva and Lausanne recruitment zones in 2000, we could not identify any mitigating effect regarding the reproduction of residential segregation also in schools. For Lausanne, a slight leveling effect can be identified by 2020.
  • The optimized catchment areas calculated for the year 2000 would have significantly increased the mix of schools in Geneva. This is particularly true for the Champel school district, which was under pressure at the time, assuming zone exchanges across school district boundaries. It would also not have required longer school routes or adjustments to school capacities.
  • Of all the cities studied, Lausanne managed to achieve the lowest mix for the year 2000, even with relaxed specifications for maximum school route lengths and school space capacities (10% leeway from the values observed in 2000). This is probably due to the rather fragmented settlement structure of the city.
  • In Geneva in 2000, the most socially charged school could not be mixed in the case of relaxed specifications (see above), because of its isolated location. The same was true in Lausanne for the most charged school in the Floréal and Pierrefleur school districts. In these cases, it would be necessary to lengthen school routes, to make routes safer, to develop school spaces and to take urban planning measures.

Recommendations of the study

  • Social mix of schools should already be taken into account in the determination of catchment areas and the allocation of schools.
  • School space planning and school building construction should be more focused on promoting social mix in urban schools.
  • Urban development policy and private and nonprofit housing construction have a central role to play in achieving mixed neighborhoods and thus mixed schools. At the same time, when modernizing neighborhoods, care must be taken to ensure that socially and educationally disadvantaged families are not pushed even further out of the city.
  • The newly developed algorithm can be integrated into the existing school allocation procedures without significantly changing the work steps of the employees in charge.
  • In order to increase social acceptance, the defined parameters of the algorithm should be disclosed in case of application, and the allocation practice of the authorities should be openly communicated.

The reform plan for Quebec

The Quebec school system was judged to be particularly segregated and inequitable in a UNESCO report published in late 2021. The coexistence of subsidized selective private high schools (79%), selective public schools with special programs charged to the parents, and the remaining public schools is denounced. The lead author of the Swiss study was therefore asked by the civic organization École ensemble to show, with hypothetical optimized recruitment zones, what an abandonment of the inequitable school system could look like. With the help of the algorithm, it was possible to create, using the example of the city of Laval, balanced recruitment zones with short school routes. These analyses are a central part of the comprehensive reform plan published by the organization on 9 May 2022. Under the plan, private schools would be free to either forgo public subsidies or fund themselves entirely with public money. All subsidized private and public schools would become neighborhood schools with an assigned catchment area. Leading experts in Quebec support the plan and there is also a great deal of public interest in it. The government representative has already signalled his commitment to improving school accessibility.

The study

Dlabac, Oliver; Amrhein, Adina; Hug, Fabienne (2022): «School mixing: more equity through intelligent school zoning. Optimized school catchment areas for Swiss cities», Aarau: Centre for Democracy Studies Aarau.

The reform plan

École ensemble (2022): «Plan pour un réseau scolaire commun», Montréal.

Dlabac, Oliver (2022): «Optimized school catchment zones for the City of Laval (Quebec)». Zurich: VILLE JUSTE.


The Center for Democracy Studies Aarau (ZDA) is a scientific research center supported by the University of Zurich, the University of Applied Sciences and Arts Northwestern Switzerland, the Canton of Aargau and the City of Aarau. It conducts basic research and deals with current questions on democracy – regionally, in Switzerland and worldwide.