This qualitative study explored Norwegian ECEC professionals' perceptions and reflections concerning the use of the Classroom Assessment Scoring System (CLASS) Pre-K and Toddler for professional development. Focus group interviews (n = 22), group interviews (n = 4), and in-depth interviews (n = 3) were conducted online. Conventional content analysis was performed using NVivo 12 software. The professionals reported that CLASS contributed to positive structures for professional community and development within which both individual and collective learning occurred. The content analysis yielded four main categories: "A shared professional platform," "Professionalisation," "Quality in practice" and "Outcomes for children and parents." The CLASS structure improved communication and collaboration between the early childhood education and care (ECEC) centres and support systems. Overall, the findings contribute to new knowledge on how ECEC professionals experience CLASS as a tool for professional development, sense of community, improved collaboration and more thoughtful classroom practice.