The reason why this study has been made is the fact that a substantial part of students in the upper secondary school changes their field of study, during or after their first year. The aim of this study is to find out the reasons behind such changes as well as finding out the affecting factors. The study has been made in two steps, first quantitatively by a poll study and the second step is qualitative by interviews. This research has been made in both private schools and municipal schools, with the ambition to search for differences between these two separate school forms. The study shows that no general differences can be found in a comparison between them. This whole study takes its viewpoint in a Social constructivistic perspective with influences from structuralism and interculturalism. The result of this study shows that the reasons that are most significant for the students who change their field of study are general discomfort with their first choice, as well as discomfort with their teachers and school friends. A to rapid study pace is also a major reason for changes The factors that have had most impact on the students are social factors like family, friends and educational guidance, and their personal feeling or intuition. In this research, comparisons between ethnicity, social status and sex have been made to reveal patterns and reasons which could have an effect on students when changing their field of study.