The increasing availability of new technologies in an ever more digitalized world has gained momentum in practically all spheres of life, making technology-related skills a key competence not only in professional settings. Thus, schools assume responsibility for imparting these skills to their students, and hence to future generations of professionals. In so doing, teachers play a key role with their competences in using new technologies constituting an essential prerequisite for the effective implementation of such skills. As models of school development and school effectiveness found teacher professionalization to be a key element with regards to student achievement as well as teachers' in-class use of new technology, the present research project conducts secondary analyses using data from the IEA International Computer and Information Literacy Study 2013 (ICILS 2013) regarding internal and external teacher professionalization. Particular emphasis is placed on the implementation of new technologies in class in a comparison between the education systems of Germany and the Czech Republic. A Latent Class Analysis serves the purpose of establishing a teacher typology with regards to technology-related professional development. This typology is subsequently used for further analyses of additional factors that show a correlation with the teachers' use of computers in class. These include the teachers' ICT self-efficacy and their emphasis on teaching ICT skills. The results show two different types of teachers across both countries. Teachers who participate in professional development use computers more frequently in class, put more emphasis on teaching ICT skills and have a stronger sense of ICT self-efficacy. When comparing teachers in Germany and the Czech Republic, teachers in Germany who participate in professional development consider themselves more ICT self-efficient, while teachers in the Czech Republic use computers more often and put more emphasis on teaching ICT skills compared with their colleagues in Germany.