Computational thinking (CT) has become increasingly important in recent years as a key competence of the twenty-first century. Referring to this development, this chapter presents research on learning and teaching of computational thinking in secondary school (grade 8) based on representative student and teacher data from the International Computer and Information Literacy Study 2018 (ICILS 2018). The research has a focus on student’s competences in computational thinking and aspects of problem-solving, mainly in Germany, but is also enriched with results in international comparison for contextualization. Besides Germany, the topic was investigated for the Republic of Korea, Denmark, the USA and Luxembourg to what extent differences in students’ competences in computational thinking can be explained by the computational thinking-related skills taught in school, considering students’ social and migration background and gender.