Various curriculum theorists and commentators have identified curriculum/instruction and the learning environment/milieu as two of the major codeterminants of students’ educational outcomes. Although learning environment is a somewhat subtle concept, considerable progress has been made over the past few decades in conceptualizing and assessing it and investigating its determinants and consequences. The learning environment is important in the curriculum field because a positive classroom environment is both a worthwhile end in its own right and a means to improved student outcomes. The field of learning environments has a rich diversity of valid and economical questionnaires that have been adapted and used in many countries. The world’s most-frequently used classroom climate questionnaire is the What Is Happening In this Class? (WIHIC) which assesses students’ perceptions of student cohesiveness, teacher support, involvement, investigation, task orientation, cooperation and equity. Other specific-purpose instruments include the Science Laboratory Environment Inventory (SLEI), Constructivist Learning Environment Survey (CLES) and Place-Based Learning and Constructivist Environment Survey (PLACES) for evaluating the unique learning environments of community-based and place-based environmental education programs. A major application of learning environment assessments is their use as criteria of effectiveness in evaluating educational programs/curricula and instructional methods/alternatives. These studies reveal that traditional curricula could be distinguished from new curricula in terms of students’ classroom environment perceptions when outcome measures cannot. Although much research has been undertaken on educational environments, less effort has been focused on helping teachers to improve the climates of their schools and classrooms. A simple approach for improving environments based on using climate surveys involves identifying and reducing discrepancies between students’ actual and preferred perceptions. Teachers who have administered these questionnaires as part of their action research typically have found that assessments of their students’ perceptions of classroom environment provide useful bases for reflection, discussion and classroom improvement.