In the school year 2023/24, the German federal state of Bavaria started teaching artificial intelligence (AI) as a new compulsory subject in the 11th grade of grammar school computer science education. The curriculum focuses on computer science related topics of machine learning and addresses the assessment of the opportunities and risks of artificial intelligence for individuals and society. The introduction of this new subject was prepared with a professional development course for all computer science teachers at Bavarian universities. We report on the structure of the professional development course at the authors’ universities and on a study, which recorded the development of teachers’ attitudes towards AI using the “General Attitudes towards Artificial Intelligence Scale” (GAAIS). As part of the four questionnaires of our longitudinal study, we also measured the development of the teachers’ self-assessment of their competences with regard to the content to be taught in the future. As is desirable for a teacher training, teachers’ self-assessment of AI competences develops positively over the course of the training. Teachers’ attitudes towards artificial intelligence were only influenced by the training in the short term, but remained unchanged at the end of the three training days.