Aiming to collect various concepts, approaches, and strategies for improving computer science education in K-12 schools, we edited this second special issue of the "ACM TOCE" journal. Our intention was to collect a set of case studies from different countries that would describe all relevant aspects of specific implementations of Computer Science Education in K-12 schools. By this, we want to deliver well-founded arguments and rich material to the critical discussion about the state and the goals of K-12 computer science education, and also provide visions for the future of this research area. In this editorial, we explain our intention and report some details about the genesis of these special issues. Following, we give a short summary of the Darmstadt Model, which was suggested to serve as a structuring principle of the case studies. The next part of the editorial presents a short description of the five extended case studies from India, Korea, NRW/Germany, Finland, and USA that are selected to be included in this second issue. In order to give some perspectives for the future, we propose a set of open research questions of the field, partly derived from the Darmstadt Model, partly stimulated by a look on large-scale investigations like PISA.