The Program for International Student Assessment (PISA) is a research project conducted by the Organization for Economic Co-operation and Development, which evaluates the knowledge and skills gained by 15-year-old students over three-year terms. Within this study's' scope, the PISA 2015 data were analysed to determine whether school-related factors [including the schools' economic, social, and cultural status (ESCS)] were related to Turkish students' science performances. Due to its nested structure, the released PISA 2015 data were analysed using the hierarchical linear model (HLM). Two models were considered to examine how Aggregated ESCS at the school level makes a difference. Thereby in model 1 shortage of educational material, staff shortage, student behaviours, and teacher behaviours were included in the analysis; in addition to these variables listed, aggregated ESCS was also added to the analysis in Model 2. The results of the analysis revealed that school-related factors--in particular, staff shortage, student behaviours, and aggregated ESCS indexes--were statistically related to students' science performances. When the aggregated ESCS was controlled, it is observed that the school-level variables had a higher effect on students' science performances.