Increasing importance is being attached to support students' learning of social-emotional and self-management skills as they may experience all kinds of difficulties and problems at school. How can teachers support students to learn useful skills to overcome these problems? The purpose of this study is to assess the effectiveness of the Skillful-Class method, which teachers can use in their classrooms to support students learn social-emotional and self-management skills in a supportive and collaborative learning environment. A Skillful-Class project was conducted in 22 Finnish and 18 Chinese primary school classes. Data was collected by pre-and post-questionnaires from autumn 2018 -spring 2019. Qualitative data was collected using a post questionnaire with open-ended questions, interviews, and discussions on webpages, which were reviewed by content analysis. There is clear evidence showing that students' skills improved significantly; further, the relationships among students, teachers, and parents also improved. The students became more supportive of and collaborative with each other. The teachers' responses also show that their work became easier at school when students learned many social-emotional and self-management skills. Based on these findings, we can conclude that the Skillful-Class method is an effective tool for teachers to help students learn skills. Further, it improves the collaboration among teachers, students, and parents, and builds a supportive and collaborative learning community.