The main objective of this paper is to investigate the effectiveness of a proposed computer-based instructional method in Primary Education for self-regulated problem solving. The proposed instructional method is based on Sternberg's model of problem solving within an authentic context. It consists of three main phases: observation, collaboration and semi-structured guidance. The ultimate learning objective is to augment the autonomous problem-solving skills of primary school children. In our study the Synergo tool was used, which is a synchronous computer supported collaborative learning tool, as well as the Moodle learning management system. The context which frames the method is authentic, very close to a students' realistic learning situation. The findings of this study advocate that students can increase their problem-solving skills in a relatively short period of time. At the same time, they can improve their approach to the solution of a given mathematical problem, performing significant signs of autonomy. (Contains 2 tables and 5 figures.)