To achieve these research objectives, the City University of New York (CUNY), Herbert H. Lehman College is partnering with New York City Department of Education Districts 7, 8, 9, 10, 11, and 12. Lehman College faculty in mathematics and mathematics education, staff of education centers and institutes who work in Bronx schools, and the Superintendents of Bronx districts work together to engage 80 experienced middle or high school teachers in the Bronx in 330 hours of professional development over 3 years to strengthen their leadership abilities, mathematics abilities, and educational practices. These MTTI teacher participants are further supported on-site at their schools and through on-line discussion forums and are provided opportunities to showcase their work. MTTI cultivates a professional network of mathematics teacher leaders who provide leadership to 200 additional middle and high school mathematics teachers as they enact a variety of roles including mentor, peer coach, presenter, conference participant/speaker, and active member of school curriculum and professional development teams. Additionally, they participate in local and national discussions of current policy, practice, and research, and they develop informed understandings of the strengths and challenges of culturally and linguistically diverse classes. Upon completion of the Institute, participants receive a Certificate for Secondary-School Mathematics Specialists through CUNY's School of Professional Studies of the Graduate School and University Center, registered with New York State Education Department.