This article illuminates factors predicting students' intention to leave upper secondary school. The research is anchored in an ecological theoretical perspective that considers dropout as a multifaceted phenomenon that culminates in the decision to leave school. Based on this, we have used a longitudinal research design to investigate to what extent factors related to students' experiences predict their intention to leave school early. The sample in this study comprises 1695 students from upper secondary schools in the county of Trøndelag in Norway. We ran descriptive analyses, correlations and hierarchical regression to analyse our data. In the stepwise causal modelling, the independent variables were placed in the same order as the hypotheses were formulated. This enabled us to test each of the independent variables to explain how much variance there was in the dependent variable (intention to leave) beyond those entered in the previous steps. The results show that the students' grades from elementary school, parental and teacher support and school engagement in upper secondary school are important explanatory factors leading to dropout. Loneliness at secondary school and students' ability to cope with stressful life events seem to be the two most important predictive factors in relation to the students' thoughts about leaving.