This study examined elements of the climate of middle-grades schools that are associated with schools' effectiveness in terms of the engagement and achievement of their students, with special emphasis on gender equity. Drawn from the National Educational Longitudinal Study of 1988, data on 9,020 eighth graders from 377 middle-grades schools were used to examine student-level variables, such as achievement, engagement, socioeconomic status (SES), and academic background; and school-level variables, such as school composition and structure, teaching and learning climate, and normative climate. Observed gender differences in outcomes were small to moderate, favoring girls as well as boys. Climate effects are stronger for effectiveness than for equity. Teaching and learning climate effects, although modest, favor a flexible curriculum organization and authentic instruction. More substantial effects accrue from elements of normative climate, particularly academic orientation, safety, and order. Composition and structure effects are strong, particularly on reading achievement. Not all climate elements that positively influence effectiveness also induce gender equity. Implications for policy and school reform are discussed. (A description of the variables used in the study is appended. Contains 67 references.) (Author/MDM)