Various school transitions provide both challenges and opportunities for pupils. The ways in which pupils cope with these transitions can have a significant impact on their everyday lives and futures. This study focuses on exploring the kinds of transitions pupils face during their comprehensive school path. The aim is to gain a better understanding of horizontal and vertical school transitions faced by Finnish ninth graders (n = 518) who are 15- to 16-years-old during their school careers. These transitions are empirically examined through two complementary aspects: (1) determining the horizontal and vertical transitions in the pupils' school career; and (2) identifying the challenges faced by the pupils in these transitions. By introducing a horizontal and vertical school transition model and exploring the transitions in this framework we aim at contributing to breaking down the complexity of the transfer process. (Contains 1 table and 3 notes.)