Compared to other countries, Germany is considered to have a relatively small private school sector. At the primary level, the vast majority of students attend a public (governmental) school, whereas only four percent of the children are enrolled in a private (non-governmental administered) school (Statistisches Bundesamt, 2021). An important feature of Germany’s private schools is that they receive large public subsidies (Nikolai & Helbig, 2021). They have permission to additionally charge school fees but are legally obliged to stay potentially affordable for every family (Klemm et al., 2018).

Like in many other countries, private school attendance has increased during the last two decades (Nikolai & Koinzer, 2017). This increase is especially steep in East Germany and in urban areas (Koinzer & Mayer, 2015). The expansion of Germany’s private school sector is critically discussed among politicians and researchers. Some authors even argue that the actual school fees are often too high and that the legal precept of social accessibility is violated. According to these authors, private schools selectively attract children from families with a higher socio-economic status (SES) who utilize private schooling as a means of social distinction (Wrase & Helbig, 2016). Consequently, private schools are assumed to be one main driver of socio-economic segregation processes in the German school system (Nikolai & Helbig, 2021).

Indeed, several studies have shown that German private schools are selective with regard to the SES of their students (Klemm et al., 2018). However, to our knowledge, no study has directly addressed the research question of whether and to what extent private schools drive socioeconomic segregation processes in the German school system. The present study investigates this desideratum by analyzing socioeconomic segregation at the primary level, where private schools are often the only school-choice alternative to the public school the students are assigned to by default (Jähnen & Helbig, 2022).

The study is based on data from two large-scale educational studies conducted in 2016 and 2021. For each student, these datasets provide information on the HISEI value (Highest International Socio-Economic Index of Occupational Status) as a well-established measure of the family’s SES. The study reports the results of descriptive analyses on the average HISEI values of public and private primary school students and school-level intraclass coefficients (ICC) for the HISEI values as an indicator for socioeconomic segregation.

Consistent with other studies, the results of our descriptive analyses show that students from private schools have, on average, a higher SES than students from public schools (e. g. MD₂₀₂₁: 8.76 HISEI-points, p = 0.002). For urban areas and in East Germany, this difference is even higher (e. g., city-states: MD₂₀₂₁: 11.48 HISEI-points, p< 0.001; East German States: MD₂₀₂₁: 12.35 HISEI-points, p< 0.001). However, when examining the distribution of the school-level-averaged HISEI values across schools, we found that for public schools, the range of this distribution is exceptionally large and almost totally overlaps the distribution for private schools. In line with this, the estimated ICCs indicate that the socioeconomic segregation within the group of public schools (e. g. 2021: ICC_{public, within} = .182) exceeds the segregation between public and private schools (e. g. 2021: ICC_{public/private, between}= .081). Taken together, this result pattern suggests that private schools only seem to have a minor effect on the socioeconomic segregation of the whole school system (ICC_{public/private, within}= .186). However, divergent results were found for East Germany (but not for the city-states). In this subsample, the estimated ICCs indicate a considerably higher segregational effect of private schools on the school system (e. g. 2021: ICC_{public, within} = .120; ICC_{public/private, between} = .191; ICC_{public/private, within}= .130).

Our analyses are based on data from the IQB Trends in Student Achievement 2016 (Stanat et al., 2017) and 2021 (Stanat et al., 2022) – two German-wide, representative large-scale studies that assessed the language and mathematical proficiencies of fourth-grade primary school students. Altogether, both datasets gathered data from 50.456 fourth-grade students from 2669 public and 77 private primary schools. As a particular feature of the study, we investigate the socioeconomic segregation of schools based on a metric variable – the HISEI values of the students. We used the imputed HISEI values provided in both datasets to deal with missing values. In reference to Merlo et al. (2005), we fitted several two-level null models using the lme4-Package (Bates et al, 2014) in the statistical software R to obtain ICCs. In our study, these coefficients represent the degree to which students are clustered within schools according to their SES and hence serve as an indicator of socioeconomic segregation in the German primary school system. To investigate the effect of private schools on segregation, we first conducted descriptive analyses focusing on the distribution of HISEI values across students and schools. In the second step, we decomposed our segregation indicator following the methodical strategy suggested by Clotfelder (2004). Accordingly, we estimated coefficients for the whole sample (public and private schools, ICCpublic/private, within), as well as separately for public schools (ICCpublic, within) and private schools (ICCpublic, within). In addition, we estimated null models with school type (public vs. private) as cluster variable (ICCpublic, between). To enable inferential statistics, standard errors for each ICC were calculated through bootstrapping. For the last two decades, official statistics show that the share of private schools has increased, particularly in urban areas and in East Germany (Koinzer & Mayer, 2015). Since this development may have resulted in a school landscape different from other parts of Germany, we additionally calculated ICCs for the subsample of the three city-states of Berlin, Hamburg, and Bremen, as well as for the five East German states. To check for the robustness of our findings, we conducted our analyses for the 2016 dataset as well as for the 2021 dataset (and found virtually no differences).

Altothegeter, the present study confirms that German private primary schools are selectively composed with regard to the SES of their students. Furthermore, our results indicate that private schools reinforce social disparities within the German school system. However, the present study also reveals that private schools only play a minor role for the socio-economic segregation in the German primary school system. Instead, our findings indicate that the public primary school sector itself is characterized by vast social inequalities. Presumably, these inequalities are primarily driven by socioeconomic residential segregation. This term refers to the spatial separation (or uneven distribution) of households within a geographical area by income, education, and occupation (Jähnen & Helbig, 2022), which has largely increased in Germany’s cities within the last decades (Helbig & Jähnen, 2018). This residential segregation directly affects school composition (e. g., schools in socially privileged areas have a far larger share of high-SES students than schools located in socially deprived areas). In conclusion, the present study suggests that it is short-sighted to restrict discussions on social inequalities and socioeconomic segregation in the German school system to the expanding private school sector. The socioeconomic segregation of the public school sector appears to be a far more significant challenge to educational equity. Innovative and wide-ranging political efforts are needed to address this challenge effectively. Furthermore, our results indicate that private schools play a different role within the school landscapes of the East German states. Future research should target this finding and analyze in more depth the sources and mechanisms of socioeconomic school segregation in these states.

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