The PISA index of economic, social and cultural status (ESCS) is a composite score derived from three key variables related to family background: parents’ highest level of education in years (PAREDINT), parents’ highest occupational status (HISEI), and home possessions (HOMEPOS).
Parents’ highest level of education in years: Students’ responses regarding their mother’s and father’s education were classified using ISCED-11 (UNESCO-UIS, 2012[20]). The index of highest education level of parents (HISCED) corresponds to the higher ISCED level of either parent. Additionally, this index was recoded into estimated number of years of schooling (PAREDINT). The conversion from ISCED levels to year of education follows an internationally standardized approach, consistent across all countries. This conversion was established based on the cumulative years of education values assigned to each ISCED level in PISA 2018. Further details on this correspondence can be found in the PISA 2022 Technical Report (OECD, 2024[19]).
Parents’ highest occupational status: Occupational data for both the student’s father and mother were obtained from responses to open-ended questions. The responses were coded using four-digit ISCO codes (ILO, 2007) and then mapped to the international socio-economic index of occupational status (ISEI) (Ganzeboom and Treiman, 2003[21]). In PISA 2022, the 2008 version of ISCO and ISEI were used. Three indices were calculated based on this information: father’s occupational status (BFMJ2); mother’s occupational status (BMMJ1); and the highest occupational status of parents (HISEI), which corresponds to the higher ISEI score of either parent or to the only available parent’s ISEI score. For all three indices, higher ISEI scores indicate higher occupational status.
Home possessions (HOMEPOS) is a proxy measure for family wealth. In PISA 2022, students reported the availability of household items at home, including books at home and country-specific household possessions identified as relevant indicators of family wealth within their national context. HOMEPOS summarizes all reported household and possession items into a single index.
For the computation the PISA index of economic, social and cultural status (ESCS), missing values for PAREDINT, HISEI or HOMEPOS were imputed using predicted values supplemented by a random component, based on a regression involving the other two variables. If data were missing for more than one of the three components, ESCS was not computed, and a missing value was assigned.
In PISA 2022, ESCS was computed by attributing equal weight to its three standardised components. These three components were standardised across the OECD countries, with each OECD country contributing equally to the calculation. The final ESCS variable was transformed so that a score of 0 represents the average OECD student, and 1 corresponds to the standard deviation across equally weighted OECD countries.