This book reports a two-year examination of a science mentoring program for seven beginning elementary school teachers in terms of their students' perceptions of classroom learning environment, achievement and attitudes, as well as these teachers' attitudes. The What Is Happening In this Class? Questionnaire (Fraser, Fisher, & McRobbie, 1996), assessing student perceptions of seven dimensions of the classroom learning environment, was modified and administered to 573 students in Grades 3-5. This research represents one of the few learning environment studies that have investigated the efficacy of mentoring programs for beginning elementary school teachers. It is also one of the few studies of mentoring to adopt a learning environment framework. The study is particularly significant and distinctive because of its focus on the impact of professional development on the changes in teaching behaviors and student outcomes in the mentored teachers' classrooms.