All of our students deserve well-trained teachers, but high needs schools often struggle to retain teachers, especially in math and science. I was lucky to work for 18 years with a remarkable group of teachers at Bret Harte Middle School in Oakland. Nine years ago, our science and math departments were struggling with turnover, so we applied and received a state grant to improve instruction. We assigned each new teacher an experienced colleague to serve as their informal mentor, and we met several times a month to share and learn together. We conducted lesson study, developing lessons together, then observing one another teach. We looked hard at our assessment practices, and learned to do formative assessments. There were several keys to making this work. 1. Classroom teachers were in charge. We set the direction of the project, and we chose the tools we would use to collaborate. We had a vision for what we needed and we owned the process. 2. Our principal, Mary Hamadeh, was supportive but not prescriptive. She encouraged us to apply for the grant, but she did not attempt to micromanage it. 3. We brought in resources from partners in the community. Local experts in Lesson Study from