Students who have more effective teachers are more likely to attend college, earn a higher salary, and live in higher socioeconomic neighborhoods (Chetty, Friedman, & Rockoff, 2012). As such, teacher effectiveness is critically important, and identifying teachers who demonstrate high potential for growth in their first year of teaching could be a real asset to the districts in which they teach. The purpose of this project is to determine which teachers seem to measurably improve their instructional practice over the course of their first-year, measured via a series of observations conducted by normed observers using a common rubric. Data came from 965 first-year teachers recruited and trained by alternative certification programs in 15 geographic regions: Delaware; Baltimore; Washington, DC; Chicago; Charlotte; Nashville; Memphis; Texas (Fort Worth, Dallas, Austin, and San Antonio); south Louisiana; and Georgia (Augusta, Savannah, and Southwestern districts). Teachers taught in all grades from kindergarten-grade 12, and taught in a variety of content areas including math, English/language arts, physical sciences, special education, and foreign languages. All teachers included in this study were participating in a one-year evaluation of classroom performance ultimately leading to a decision regarding whether or not to recommend the teacher for state certification. Study findings showed that teachers vary meaningfully in their classroom performance in their first year of teaching. Early proficiency was the best predictor of overall performance, suggesting that interventions could be targeted early in the year to support teachers who are struggling from the beginning of assuming responsibility for their own classroom. Teachers who seemed adept at facilitating student centered-lessons appeared able to achieve more growth in performance than their peers who struggled at this competency. Further, math teachers seemed to perform less well than teachers in other subjects, suggesting that either (1) the rubric (or observers) is not well equipped to assess math performance; or (2) math teachers recruited and trained by these certification programs are not receiving the necessary supports to perform well in the classroom. A sample observation report and a table are appended.