What Makes a Classmate a Peer? Examining Which Peers Matter in NYC Elementary Schools

We identify and estimate the effects of student-level social spillovers on standardized test performance in New York City (NYC) elementary schools. We leverage student demographic data to construct within-classroom social networks based on shared student characteristics, such as a gender or ethnicity. Rather than aggregate shared characteristics into a single network matrix, we specify additively separate network matrices for each shared characteristic and estimate city-wide peer effects for each one. Conditional on sharing a classroom, we find that the most important student peer effects are shared ethnicity, gender, and primary language spoken at home. Identification of the model is discussed