The Classroom Video Analysis (CVA) instrument is a new and innovative approach to measuring teachers' Mathematics Knowledge for Teaching (MKT). The MKT of teachers is a key indicator to monitor according to the National Academy of Science report Monitoring Progress toward Successful K-12 STEM Education. The most common approach to assessing MKT are the multiple-choice measures developed by Ball and Hill, which in some studies have been shown to correlate significantly with instructional quality or student learning. While the measures clearly represent significant improvements over traditional tests, they are not without limitations. Correlations between MKT scores, instructional quality and student learning have been inconsistent across studies. The CVA provides an innovative alternative. In the CVA teachers view short video clips of authentic mathematics instruction online and analyze them in writing. Based on early work, teachers' CVA scores were not only reliable and predicted the MKT, but were also better predictors of instructional quality and student learning. One advantage of the CVA is that analyzing teaching events is closer to the work of teaching itself and hence less onerous for teachers and easy to embed. Most recently, research has shown that the CVA can be computer scored, making it potentially highly scalable. This project will develop an extension of the measure that is aligned with the Common Core State Standards (CCSS), and then assess its feasibility as a scalable indicator of MKT. Findings from this study will help evaluate the feasibility of developing video-based MKT measures that are classroom-focused and seek to approximate as much as possible the knowledge that is used in the process of teaching. Findings will inform which item prompts and formats appear to be most promising as indicators of standards-based MKT. The research team hypothesizes that the knowledge teachers draw on when analyzing the teaching events in the video clips is their usable MKT not just knowledge they can access on a test but knowledge they can activate and apply in the classroom. Previous work was based on general prompts and rubrics. This project will map existing CVA fraction clips onto the CCSS, including the mathematical practices. The project will revise the tasks posed and the scoring rubrics applied to create classroom-focused, standards-based measures of MKT that can be used to monitor this indicator. Next to more general prompts they will develop content-specific ones, using different item formats and ways of scoring. The project will complete preliminary testing of new measures in two stages. First, the project will collect and analyze responses from 100 mathematics teachers (grades 3-5) using different versions of the new standards-aligned items and evaluate item and scale functioning and score reliability. The project will also explore how teachers' scores on our new measures relate their scores on a traditional MKT fraction scale. In a second study of 40 mathematics teachers and their grade 3-5 students, the project will combine the well-working items from the first study into new scales and explore how they relate to the traditional MKT and student learning of fractions. The project will analyze the items and scales using classical test theory, item response theory models, and explore the applicability of diagnostic classification models.