This study examined the reliability and structure of the Classroom Assessment Scoring System (CLASS; Pianta, R. C., K. M. La Paro, and B. K. Hamre. 2008. "Classroom Assessment Scoring System. Manual Pre-K." Baltimore, MD: Brookes) and the quality of interactional processes in a German pre-school setting, drawing on a sample of 390 children in 61 language promotion groups. Rater agreement, temporal stability, and internal consistency were used to describe the reliability. Confirmatory factor analysis was used to investigate the three-factor structure of CLASS with the domains: "Emotional Support," "Classroom Organization," and "Instructional Support." The analysis revealed that reliable assessments of the quality of classroom interactional processes could be achieved and that the three-factor structure could be modelled in a German pre-school setting. The examination of the quality of classroom interactional processes in these language promotion groups indicated that "Emotional Support" and "Classroom Organization" were excellent but that the quality of Instructional Support was very low. Consequences of this study were discussed.