This qualitative study, carried out in an early learning center in an international school in Japan, aims to examine the place, meaning, and practice of assessment of young children’s learning through the methodology of documentation as defined and developed by the educators of the Reggio Emilia Approach. Whereas most aspects of instruction and assessment practices focus on individual performances and achievements, this study looks at the learning strategies of young children within the group and the learning of the group and the complexities of assessment practices assigned to socio-cultural theory. The focus of this study, therefore, is framed within socio-cultural theory to look at the intersection of the two, that of group learning and documentation, where the systematic and purposeful documentation of the ways in which groups develop ideas, theories and understanding is given space as being critical to learning of individuals as well as of groups towards building an understanding of assessment from a socio-cultural perspective. Learning is viewed as relevant to experience where the relations between the social and personal (cultural) are shared and that each person learns autonomously and through the ways of learning of others. The study was carried out in the form of action research in the course of one academic year, with the researcher acting as an active participant observer to a group of 4 children and a teacher who formed a learning group through a yearlong project on the concept of color. The teacher was asked to document the process of the salient paths of learning of the children through the project, becoming the ‘documentor’ of the project, and the researcher ‘documenting the documentor’. The main findings suggest to view learning of young children as a web of reciprocal expectations and possibilities of engagement built upon children’s constant mediation between scientific and everyday concepts with and through others.