In a democratic society, school has the goal to foster democratic attitudes in students. Besides explicit attempts to do so, justice experiences in school may be crucial to develop positive attitudes towards democracy. Therefore, we studied the relationship between different dimensions of justice experiences in school and democratic attitudes. We further examined a potential mechanism underlying this relationship, namely general trust, and hypothesized that the relationship between justice experiences in school and democratic attitudes can be understood on the basis of social exchange theory. A total of 210 participants who had visited a public school gave information about their justice experiences in school, general trust, and democratic attitudes. First, it was shown that overall experiences of distributive and interactional justice predict democratic attitudes, more specifically the approval of civic and human rights and the approval of the democratic institutions. Second, we found that the relationships between overall distributive and interactional justice and the approval of civic and human rights, the approval of the democratic institutions, and the approval of democracy-supporting behaviors are each mediated by general trust which can be interpreted as a social exchange process. This study therefore highlights the role of general justice-related school experiences for the development of democratic attitudes.