The research goal is to check implementation of assessment principles in practice in children and youth behaviour. A sample of research consisted of 20 Opinions and suggestions and three social pedagogues witch are employed at the Department of team assessment / diagnosis at the Community Services Center, Zagreb. The sample of Opinions and proposals covered the time period from 2013 to 2018 year. For the content analysis of Opinions and suggestions it was used so-called focused content analysis and for result interpretation of focus group it was used inductive thematic analysis. In the research results trough five categories and 15 subcategories is described which principles of assessment are represented in the Opinions and proposals and how they are operationalized. While the focus group results gave an insight into the understanding and experience of social pedagogues related to the assessment principles and their recommendations for further application and are described in five themes. The results indicate that in the Opinions and proposals are used the evaluation principles which literature implies. On the other hand, the focus group results also point to an understanding of the principle in accordance with literature. The research has provided additional insight and understanding for this topic and can serve as an incentive for further research to deeper into this topic, as well as to set standards for their application at the national level of science, profession and practice.