The purpose of the study was to examine the relations among a single item school readiness screener, social/emotional ratings, and academic performance. A prior study found that single item kindergarten readiness ratings completed in the fall predicted end-of-year academic and behavior outcomes even after controlling for baseline scores. Here, we attempted to extend these findings by using a single overall readiness item, an expanded rating scale for the item, and a comparison with other social and emotional ratings provided by teachers. Fifty-five teachers in 18 elementary school sites completed the overall readiness item on 893 kindergarten students. Teachers also completed Likert-type social emotional items and assessments of emergent literacy skills on all students. Results suggested that teachers use basic social behavior expectations in their judgments of readiness rather than extreme disruptive behaviors. In addition, the single item identified students who were below benchmark and not prepared to start school with higher accuracy than a 14-item social rating scale. Discussion focuses on the promise and limitations of the single item measure and future directions for its study and use.