In recent years, physical computing has grown in popularity for school education. Children and teenagers learn basic concepts of embedded systems in a creative and motivating manner. We investigate teachers´ expectations towards and first experiences with physical computing to gain a better understanding of their needs in professional development. We developed, conducted and evaluated a qualitative interview study, identified typical benefits (e.g. motivation, direct feedback and tangibility), topics (e.g. algorithms and data structures) and challenges (e.g. acquisition of suitable hardware and necessary preparations) that teachers associate with physical computing and derive recommendations for professional development and supporting measures.