The Dalton Plan as a system of instruction has been in operation since 1922 in a Sydney school. A description of the Dalton Plan, in principle and practice, and an analysis of the Dalton Plan into components was undertaken, based on data collected from several sources, namely 16 staff interviews, 30 student interviews (Year 7 n= 15; Year 11 n=15), student observations (n=30), a student questionnaire on planning and hours (Year 7 n=20; Year 11 n=20) and record of study (Year 11 n=15). Effectiveness was considered in terms of academic achievement and in terms of student use of self- regulated learning strategies. Students at the Dalton Plan school were compared to students at a conventional school whose student population was very similar to that of the Dalton Plan school in general ability and socioeconomic status. It was found that students at the Dalton Plan school achieve academically at the same level as students from a conventional school, as measured by the Higher School Certificate best ten aggregate.