Problem Statement: Preservice teachers acquire the knowledge and skills needed for elementary mathematics education by themselves obtaining quality university educations and by being actively involved in mathematics. Thus, it is essential to make room in teacher education for student-centered projects and activities. Purpose of Study: This study aimed to reveal whether using student-centered project-and activity-supported practices in the course "Mathematics Education II" had an effect on preservice teachers' achievement, as compared to teacher-centered education. It also aimed to identify student views on these two student-centered practices. Methods: Conducted during the 2009-2010 academic year, the study was designed as a pretest-posttest control group experimental study with third-year teaching students in the Department of Elementary Education, Division of Classroom Education at an Ankara university. To compare student achievement on four of six subproblems, the "Measurement and Geometry Education Test" was used. Data were analyzed using a t-test and one-way analysis of variance. For the fifth and sixth subproblems, student views on the different practices adopted in two student-centered groups were collected with the help of two open-ended questions, and content analysis was performed on the resulting qualitative data. Findings and Results: The first three subproblems examined whether a difference existed between each group's "Measurement and Geometry Education Test" pre and posttest mean scores. A difference in favor of the posttest was found in all three groups, i.e. between the student-centered Groups 1 and 2 and the teacher-centered Group 3. In the fourth subproblem, a meaningful difference was found between the mean achievement scores of the teacher-centered control group and the student-centered project-and activity-supported groups. However, there was no such difference between the mean achievement scores of the two student-centered groups. Although project and activity group students supplied many positive comments on the process, they also expressed some criticism. Conclusions and Recommendations: It is satisfying that student achievement on the "Measurement and Geometry Education Test" was meaningfully higher at the end of instruction in all three groups. The results favored student-centered project and activity-supported instruction. Using projects or activities in classes positively affected student success. While the project-supported group mostly made positive remarks about group work and project preparation, the activity-supported group mostly made positive remarks about preservice teachers' mathematics education knowledge and skills.