This study examined the influence of a professional development program based around commercially available inquiry science curricula on the teaching practices of 27 beginning elementary school teachers and their teacher mentors over a 2 year period. A quantitative rubric used to score inquiry elements and use of data in videotaped lessons indicated that education students assigned to inquiry-based classrooms during their methods course or student teaching year outperformed students without this experience. There was also a significant positive effect of multi-year access to the kit-based program on mentor teaching practice. Recent inclusion of a "writing in science" program in both preservice and inservice training has been used to address the lesson element that received lowest scores--evaluation of data and its use in scientific explanation.