This report is the fifth in a series examining the magnitude of the teacher shortage and the working conditions and other factors that contribute to the shortage. The series finds that the teacher shortage is real, large and growing. When indicators of teacher quality (certification, relevant training, experience, etc.) are taken into account, the shortage is even more acute than currently estimated, with high-poverty schools suffering the most from the shortage of credentialed teachers. This report examines the early career supports available to novice teachers in the first year of their careers, as well as the continued learning opportunities available to teachers throughout their careers. It also explores the extent to which certain aspects of the working environment--the presence or absence of supportive and collaborative relationships; cooperation among teachers, colleagues, and principals; and teachers' influence over policy and day-to-day classroom decisions--establish a culture of learning in which teachers' knowledge and professionalism are recognized and cultivated.