The purpose of the research was to determine the effectiveness of the pedagogical strategy the forum to develop the critical thinking skills of the eleventh grade students in the area of Social Sciences at the Algarrobo Departmental Educational Institution; the methodology used a quasi-experimental design with a control and experimental group, with Pretest and posttest. The students were intervened in the third period of the year 201. To contribute to the potentialization of thought was based on the skills proposed by Peter Facione (2009): Interpretation, Explanation, Analysis, Inference and Evaluation to measure a questionnaire was used, the results of this investigation allowed to verify that when making the forums contributed to increase the level of critical thinking development of the intervened students, that is, significant differences were found in the level that the experimental group had before and after being intervened. In the same way, it was evident in their opinions and arguments as the intervention process progressed in relation to describing situations, beliefs, events; clarification of meanings; examine ideas, identify and analyze arguments, question evidence, assess opinions and propose alternatives; showing a reflective and reasoned thought