The Preschool Educational Environment Rating System (PEERS) is a measure designed to examine the quality of instruction in preschool settings. Unlike other rating scales, it not only measures the environment, it also examines both how teachers construct their classroom for instruction and the quality of the enactment of instruction. Designed on behalf of the Albert Shanker Institute for a collaboration with the Saint Louis Public School System (SLPSS), the PEERS is an evidence-based measure that can be used as an observational tool by administrators to more fully understand and assess the environments and instruction they provide to their students, with the ultimate goal of improving children's academic outcomes. This document provides the following: (1) Background on PEERS; (2) Description of the Measure; (3) PEERS Categories descriptions: (a) Environment; (b) Instruction; and (4) Benefits of PEERS.