Schools committed to equity are experimenting with creative and powerful ways for teachers to ensure all students receive what they need to learn in the classroom. Many of these efforts focus professional learning on strengthening the instructional core -- teachers' knowledge of and relationships with students, teachers' deep and critical knowledge of the content, and the ways teachers make that content relevant to students. This article discusses how when teachers' learning takes the form of collaborative inquiry, it produces a wealth of evidence and insight that not only helps teachers transform their teaching practice, but is also invaluable for identifying the school conditions needed to support that transformation. School leaders have much they can learn from teachers' collaborative inquiry if they are prepared to do so.