The vast majority of Michigan's teachers work above and beyond their required work week; the average teacher works more than 45 hours per week. The time teachers spend outside regular school hours is often ignored by critics who deride the "short hours and long vacations" enjoyed by teachers. When discussing compensation policies and changes to the school year, policymakers need to consider the hours that teachers already spend working after the bell signals the end of the school day. Many factors influence the hours teachers spend working each week. School and organizational factors that are correlated with differences in teacher work weeks may be amenable to policy intervention. For example, the fewer hours worked by teachers in schools with high concentrations of poor and minority students in urban areas may highlight the need for more targeted pay incentives for teachers in those schools and the need for greater funding for extracurricular activities in those environments. Further, the differences attributed to individual teacher variables, such as years of experience and gender, may be influenced by the different expectations and incentives that they face. Relatively inexperienced teachers may be expected to take on responsibility for various school initiatives and student activities, despite the fact that they also need more time for instructional preparation than their more experienced peers. The amount of time teachers spend working outside school hours on activities such as preparation, grading, attending meetings, and talking with parents is noteworthy. Teachers often put in this time without receiving financial compensation for their efforts. If policymakers are concerned with the inequalities in the number of hours teachers spend in these activities across levels of poverty, minority enrollment and school community type, then perhaps they could restructure the teacher work week to include more time in the required--and compensated--working hours. For example, schools and districts could reorganize and possibly lengthen the school instructional day to provide teachers with more time for planning and grading within the school day. The data presented in this report suggest that the organizational conditions of schools influence the number of hours that teachers work each week and the types of activities on which they spend their time. The expectations, incentives and constraints that define the conditions under which teachers make decisions vary across schools. These differences have implications not only for teacher recruitment and retention in schools, but also for the instructional and extracurricular experiences students have in schools. (Contains 8 tables and 6 footnotes.)