In Germany schools are obliged to foster students' digital competences. Based on the proficiency levels of students' computer and information literacy (CIL) from the International Computer and Information Literacy Study (ICILS 2013), and a theoretical approach to media education in school, this paper aims to provide evidence on the relevance of teacher- and school-related factors in the fostering of students' CIL. On the basis of a representative sample of secondary school teachers in Germany a structural equation model (SEM) which accommodated the frequency of ICT-use in instruction as a mediator variable was computed. The results of the SEM indicate teachers' attitudes towards the use of Information and Communication Technologies (ICT) in instruction, ICT-related collaboration, and sufficient ICT equipment at schools as significant predictors in fostering students' CIL. Findings bear important implications for teacher education in terms of preparing teachers for this fundamental task.