In many countries, out-of-school tutoring in academic subjects has become a widespread phenomenon that affects high proportions of students. Scholarly literature has considered various determinants of participation in such tutoring, but school quality has as yet been rather neglected. The aim of the study is to explore the relationship between the quality of school instruction and perceived learning environments on the one hand, and participation in additional instruction in science on the other. Using the Programme for International Student Assessment (PISA) 2015 dataset, we analysed data on five post-socialist countries (Bulgaria, Croatia, Hungary, Poland, and Slovakia). By employing two-level logistic regression models, we estimated the probabilities of taking additional instruction in science in and outside of the school building. Different aspects of learning environments as perceived by students have a somewhat indirect influence, which is mediated through the students’ individual performance in science. Except in Bulgaria, school overall achievement is not related to taking additional tutoring.