This study investigates the impacts of a year-long professional development program on Kindergarten teachers' beliefs and practices and the association of these changes with student achievement in mathematics measured by curriculum-based instruments. Although teacher content knowledge was not statistically significantly different before and after participation in the program, changes in teachers' beliefs and practices were both noticed: a trend towards discovery/connectionist orientation and student-centered practices. Teachers' gain scores on a measure of mathematics content knowledge was positively related to the linear growth rate of student achievement.