As societies the world over move towards defining inclusive and effective education systems this presents the educator with the new challenge of providing an equal and democratic education environment for all students. With children the nature of functioning and environmental settings varies greatly in comparison with adults and assessing children’s involvement in activities is of particular importance to ensure effective and inclusive society building through education. Building on the existing and previous participation research this thesis specifically aims to provide a means to theorize participation from two perspectives (frequency of attending and intensity of involvement) and put in to operation using five dimensions of the environment: availability, accessibility, affordability, accommodability, and acceptability. Contextually this has been done by investigating children in need of additional support (including children with disabilities) at school. Results indicate that while research and theory take a holistic and balanced approach by using participation based on two perspectives, this has yet to filter down to practice. A new approach to measuring inclusive education using social capital, the five environmental dimensions, and the ICF-CY is proposed and tested. However, while the ICF-CY provides a consistent descriptive framework, no clear connections between social capital and inclusive education policy could be drawn and the five environmental dimensions – especially the involvement-related ones – need further development. The final paper presents evidence from the individual perspective for a third ICF-CY activities and participation qualifier to represent the subjective experience of involvement. Participation can thus be regarded as a multi-dimensional phenomenon with two main conceptual roots: sociology and developmental psychology. / MURINET project (Multidisciplinary Research Network on Health and Disability in Europe, European Commission project funded within the Sixth Framework Programme, MRTN-CT-2006-035794).