Eric Hanushek and Steven Rivkin examine how salary and working conditions affect the quality of instruction in the classroom. The wages of teachers relative to those of other college graduates have fallen steadily since 1940. Today, average wages differ little, however, between urban and suburban districts. In some metropolitan areas urban districts pay more, while in others, suburban districts pay more. But working conditions in urban and suburban districts differ substantially, with urban teachers reporting far less administrator and parental support, worse materials, and greater student problems. Difficult working conditions may drive much of the difference in turnover of teachers and the transfer of teachers across schools. Using rich data from Texas public schools, the authors describe in detail what happens when teachers move from school to school. They examine how salaries and student characteristics change when teachers move and also whether turnover affects teacher quality and student achievement. They note that both wages and student characteristics affect teachers' choices and result in a sorting of teachers across schools, but they find little evidence that teacher transitions are detrimental to student learning. The extent to which variations in salaries and working conditions translate into differences in the quality of instruction depends importantly on the effectiveness of school personnel policies in hiring and retaining the most effective teachers and on constraints on both entry into the profession and the firing of low performers. The authors conclude that overall salary increases for teachers would be both expensive and ineffective. The best way to improve the quality of instruction would be to lower barriers to becoming a teacher, such as certification, and to link compensation and career advancement more closely with teachers' ability to raise student performance. (Contains 5 tables, 1 figure, and 35 notes.)