Introduction: The present study analyzed differences between boys and girls in articular width throughout school life. Methods: We analyze a population of 420 boys and girls aged between 7 and 17 years old (primary and secondary education). A battery of tests evaluating flexibility through goniometric measurements was carried out. This battery consisted of 10 tests, from which data related to the articular mobility of the shoulders, hip, knee and ankles were gathered. Results: The results obtained indicate that articular width in the subjects studied decreases with age. The results were better in girls than in boys, with substantial differences in three of the elements included in the test. Peak reductions varied, depending on sex.