Constructing models of dynamic systems is an important skill in both mathematics and science instruction. However, it has proved difficult to teach. Dragoon is an intelligent tutoring system intended to quickly and effectively teach this important skill. This paper describes Dragoon and an evaluation of it. The evaluation randomly assigned students in a university class to either Dragoon or baseline instruction that used Dragoon as an editor only. Among students who did use their systems, the tutored students scored reliably higher (p < 0.021, d = 1.06) on the post-test than the students who used only the conventional editor-based instruction.