As teachers who care deeply about the quality of their own teaching and the development of teaching as a profession, the authors write this article from their conviction that performance assessments in teaching are a critical strategy for developing teachers' expertise and for improving the quality of teacher preparation. They note that the National Board--composed largely of accomplished teachers--was the first truly professional effort to set standards and create assessments for teaching. More than 20 years ago, the board rejected multiple-choice tests in favor of assessments of real performance. National Board portfolios combine student work samples, videotapes of instruction, and teachers' analyses to assemble a picture of teachers' practice as it is shaped by the particular needs of their students and the particular context of their schools. As in other professions, this evidence is scored by trained raters who are expert in the same field, using criteria that define critical dimensions of teaching. The edTPA, also developed by teachers and teacher educators, is built on the National Board model and subsequent work by California educators. The Performance Assessment for California Teachers (PACT) was developed by 12 public and private universities in 2002 when the state legislature required that all candidates be licensed through a performance assessment. More than 30 universities and alternative programs now use the assessment, which has proved so productive that programs have sustained it for a decade even when promised state funding never materialized. As interest spread across the country, a national version began to evolve. Instructors and supervisors continue to teach, observe, support, and evaluate candidates, as they always have. The assessment--which allows teachers to be evaluated in their own student-teaching or internship classrooms using curriculum they have designed--focuses on areas all beginning teachers need to learn: how to plan around learning goals and student needs, how to engage in purposeful instruction and reflect on the results, how to evaluate student learning, and how to plan for next steps for individual students and the class as a whole. (Contains 7 endnotes.)