Given that there is a lack of children's active involvement in the school design process, the aim of the present multimethod study was to gather data in relation to children's active involvement towards the improvement of their own school's physical environment. Over a period of three months, twenty-nine children aged 4-5 years participated in this process, using a range of methods according to the Mosaic Approach [Clark, A., & Moss, P. (2008). Spaces to play: More listening to young children using the Mosaic approach. London: National Children's Bureau Enterprises]. So, multi-faceted methods were encouraged and observations, interviews and participatory techniques such as photograph taking, maps, drawings and discussions were applied during the intervention sessions. Pre and post intervention changes concerning the quality of classroom environment were evaluated using a standardized version of ECERS-R. Results are encouraging in that children's voices can be included and therefore child-centered techniques can be implemented while using standardized measures to assess the quality of educational contexts such as the ECERS-R scale.