The topical problem of pedagogical psychology is to identify the conditions and factors of students’ personal agency development. One of the ways to solve the problem is to build adequate mathematical models. The purpose of the study is to justify the use of multimediator analysis in modelling a fractal psychological and pedagogical system so as to describe the ways and stages of students’ agency development in the course of the study. It is hypothesized that ways of performing learning actions are considered as elements of the stages of learners’ personal agency formation.