The present study was conducted to "investigate the effectiveness of Philosophy for Children education on the critical thinking skills of fourth grade elementary school students in the three dimensions of creativity, cognitive maturity, and mental engagement." In addition, the effect of this method on the critical thinking of three groups of students (strong-average-weak) was examined. From the population of fourth grade elementary school female students in District 15 of Tehran, one school was selected using a cluster method and two fourth grade classes were randomly assigned to the experimental and control groups. The research method was a quasi-experimental type with pre-test and post-test. The Ricketts Critical Thinking Questionnaire (2003) was used to measure students' critical thinking. Educational intervention in the form of the P4C method was carried out in 12 60-minute training sessions for the experimental group. The findings from the multivariate analysis of covariance (MANCOVA) test showed that the P4C method has an effect on improving students' critical thinking in three dimensions: creativity, cognitive maturity, and mental engagement. There is no significant difference in the effect of P4C training on critical thinking skills based on academic performance between average and weak students; however, there is a significant difference between strong and weak students and between strong and average students. Finally, it is emphasized that the successful implementation of this method requires simultaneous attention to educational content, teaching methods, and creating a collaborative environment that can respond to individual differences among students, and some practical suggestions are mentioned.