This study was designed to investigate the effects of a dynamic instructional environment, English proficiency, and visualization level, independently and interactively, on middle school students' construction of the concepts of reflection and rotation. The effects of a dynamic instructional environment and English proficiency on students' two- and three-dimensional visualization was also examined. The dynamic instructional environment was based on the constructivist view of teaching and learning, the need for students to work within their zones of proximal development, and the use of context-embedded situations. After controlling for initial differences, it was concluded that students experiencing the dynamic instructional environment significantly outperformed students experiencing a traditional environment on content measures of the concepts of reflection and rotation as well as on measures of two-dimensional visualization. The students' instructional environment did not significantly affect their three-dimensional visualization. There were no statistically significant differences on any of the dependent variables between the performances of limited English proficient students and those of their English proficient peers when the same instructional environment was experienced. The research demonstrated that a computer-based, dynamic instructional environment can provide for successful outcomes in LEP and EP students' learning of the concepts of reflection and rotation. Implications of the findings are discussed. Contains 39 references. (Author/JRH)