SCALE CREATION

Responses from the student background questionnaire were used to construct a scale of socioeconomic status (SES). The factors included in the construction of the scale include the number of books at home, parents’ highest level of education, parents’ highest occupational status, language spoken at home most of the time, as well as a bundle of commodities/goods for learning (e.g., availability of internet, quiet place for learning, number of ICT devices).

Rasch modelling (senate-weighted partial credit model) was used to scale. To handle nonresponse, the scale was not estimated for students who did not answer at least half of the questions included in the scale.

Multivariate imputation by chained equations (MICE) was used to assign predicted values to those students who answered more than half (but not all) questions.

The scale was rescaled so that it has an international average of 50 across all countries with a standard deviation of 10 points. Based on the distribution of the scores on the scale, the continuous scale was divided into three ordinal categories. The ordinal categories were constructed by dividing the scale into lower, middle, and upper thirds of the scale score distributions (weighted). It is thus an empirical division of cut scores rather than an interpretation of the items.

LIST OF BACKGROUND SCALES

Students’ Home Resources and Socioeconomic Background Scale (SES) - The name in the international database is

• “SES_irt” (continuous scale) and
• “SES_irt_c” (ordinal scale).