System Dynamics is a well formulated methodology for analyzing the components of a system including cause-effect relationships and their underlying mathematics and logic, time delays, and feedback loops. It began in the business and manufacturing world, but is now affecting education and many other disciplines. Having inspired by successful policy changes in lots of fields, the system dynamics researchers targeted to apply the system dynamics approach in the educational fields too. The aim of this study is to model spring mass system that is taught in middle school science and technology curriculum, using system dynamics approach and to learn the effect of the system dynamics approach with sample application group. This research consists of three sections: exploring system elements, modeling systems and testing models. In the first section of this research the theoretical information was given about how the models are developed and tested. In the other section two sample students' developmental data were examined and discussed. (Contains 8 figures.)