The core activity of a Teachers Institute takes place in seminars. Each seminar is led by a faculty member from a participating university or college, with up to a dozen Fellows, teachers from participating school districts. Local seminars will meet on a regular schedule, typically for two hours or more at one time, over a period of months. In New Haven, seminars meet in 12 two-hour sessions, running from March through early July. The National Initiative also runs seminars, for teachers from all participating districts. These National Seminars have preliminary meetings in early May, and their main work is done in a two-week Intensive Session in mid-July.The distinguishing feature of a Teachers Institute is that, rather than provide evidence of mastery of the seminar topic by examination or other means internal to the seminar, the primary obligation of each seminar Fellow is to write a curriculum unit based on the seminar. This structure obviates questions as to what seminar material is mastered by a fellow, and also the question of whether the seminar affects classroom practice: it automatically does.The Teachers Institute approach is based on a cooperative partnership between a college or university and a school district. (It is possible to have multiple partners on either side of the partnership, but for simplicity we will ignore that possibility here.) Faculty members from the higher education partner contribute their subject matter expertise by offering seminars in relevant topics, and teachers contribute their classroom expertise to create sequences of lessons that incorporate the insights afforded by the seminar. Fellows in a given seminar will typically represent all grade levels, from the primary grades through high school. It follows that seminar themes must be educationally robust: they must have potential for enriching instruction for students of all ages. Seminars can be built around recent advances in a field, especially in science or technology. They may also be built around enduring issues: important perspectives that may escape attention in standard courses, or fundamental ideas that are relatively neglected in existing curricula. The seminars offered in the National Initiative in 2011 were:The Art of Reading PeopleLove and Politics in the SonnetThe Big Easy: Literary New Orleans and Intangible HeritageChemistry of Everyday ThingsGreat Ideas of Primary MathematicsOrgans and Artificial OrgansI have been the main leader of seminars in mathematics for the National Initiative for the past several years. The seminars I have offered in previous years areThe Art and Craft of Word ProblemsEstimationThe Mathematics of WallpaperA strong feature of a Teachers Institute is the key role played by teachers in all activities. Seminar topics are offered by faculty, but the decisions as to which seminars will run is in the hands of a committee of Teacher Representatives, who canvas their colleagues throughout the district as to which of the proposed topics have the most potential to raise the level of instruction. After seminars are selected, the same committee accepts and vets applications to participate in the selected seminars, and determines seminar membership. Each seminar also has one Fellow who serves as coordinator, ensuring good communication between the Seminar Leader and the Fellows, and especially, that the complex task of unit writing proceeds on schedule, with each Fellow having adequate guidance and support.In this spirit, the seminars themselves are highly collegial affairs, with regular participation from all Fellows as well as the Seminar Leader. In particular, seminars include time for Fellows to share with each other their plans for their units, and to provide feedback and mutual support for their projects. Discussions initiated during seminar time may well lead to further exchanges between Fellows outside of seminar meetings. …