A four-year research project funded by NSF examines the efficacy of an approach to high school geometry that utilizes dynamic geometry (DG) software and supporting instructional materials to supplement ordinary instructional practices. It compares effects of that intervention (the DG approach) with standard instruction that does not make use of computer tools. This paper reports a study conducted during the second year of the project. Student learning is assessed by a geometry test and other tests. Data for answering the research questions of the study are analyzed mainly by appropriate HLM methods. The analysis on the geometry test data is discussed in detail. The experimental group significantly outperformed the control group in geometry performance.

One of the most rewarding accomplishments of working with preservice secondary school mathematics teachers is helping them develop conceptually connected knowledge and see mathematics as an integrated whole rather than isolated pieces. The NCTM Connections Standard (2000) states: “Problem selection is especially important because students are unlikely to learn to make connections unless they are working on problems or situations that have the potential for suggesting such linkages” (p. 359).
To help students see and use the connections among various mathematical between this problem situation and various mathematical topics. In addition, their explorations
of multiple approaches to proofs led beyond proof as verification to more of illumination and systematization in understandable yet deep ways (de Villiers
1999); expanded their repertoire of problemsolving strategies; and developed their confidence, interest, ability, and flexibility in solving various types of new problems. These benefits, in turn, will be passed on to their own students.