Recent studies have suggested that the professional training received by general educators does not adequately prepare them to properly implement inclusion-based practices. The idea of inclusion in practice has not significantly changed the situation of teaching pupils with special educational needs (SENs) in mainstream classes. This study's primary intent is to examine the factors that identify the school staff's ability to meet the needs of SEN pupils in their daily teaching situations. A total of 187 elementary school teachers, principals and teaching assistants in a Finnish city completed a structured questionnaire that used a self-evaluation method. Two components were generalised according to answers concerning the respondents' confidence in and knowledge of teaching SEN pupils. The results indicate that teachers' qualifications constitute the main reason affecting their ability in this area. Pedagogical and practical knowledge, as well as collaborative skills in teaching SEN pupils, is focused on special educators. These findings reveal the need for additional and in-service training and more effective cooperation between special and general education to share the knowledge of teaching SEN pupils in practice.