When the Adams 12 school district introduced a new mathematics curriculum to elementary schools several years ago, leaders have turned to an idea both old and new to make the change a success. They created a position dubbed "student-achievement coach" that gives each school a skilled teacher ready to urge her colleagues forward in three areas: putting math across, helping English-language learners in the classroom, and using assessment to improve instruction. Adams 12 is like many districts these days, investing in a teacher-coaching program even as funding challenges and a growing number of children from poor and non-English-speaking families put changes to it on the horizon. Educational fads come and go, but coaching for teachers is fast becoming a tool of choice for striving districts. This article describes how on-site coaches help districts enhance their teachers' instructional practices and improve the chances of their students' success.