This study is concerned with evaluating critical learning of 10-11 year-old students studying global citizenship through an online discussion environment. The evaluation is based on analysing the use of language as both a social reasoning tool and cognitive learning tool. Evaluation methods use: (1) content analysis of the online discussion through a dialogical framework for social modes of thinking to measure social reasoning, and (2) keyword identification and concept mapping connectivity to measure conceptual transfer from the online discussion to individual students and higher-order thinking. Triangulation of data shows that students using an online discussion forum increase the incidence of exploratory talk, broaden their knowledge of global citizenship concepts, transfer conceptual knowledge from the discussion to the individual and use higher-order thinking. The study establishes that critical learning takes place through using a collaborative online discussion forum and finds that the dialogical framework for social modes of thinking and concept mapping based on information and communication technologies provide useful evaluation tools to identify components of critical learning. (Contains 3 tables and 2 figures.)