The relationship between self-regulation, using measures from the affective and cognitive domains, and academic performance was investigated for 62 middle-school (grade 6) students. Key aspects of self-regulated learning studied were planning and self-assessment. A range of affective variables, including self-concept and locus of control, was also examined. Teachers' perspectives on students' academic ability were obtained, and standardized test scores were used as a measure of academic achievement. Findings indicate that while such metacognitive variables as planning and self-assessment abilities were significantly related to achievement in mathematics, reading, and science, student and teacher perceptions of scholastic ability were more salient factors in predicting academic performance. The locus of control variable did not appear to have much utility in predicting classroom grades and performance on standardized measures of achievement. Implications of these findings for educational practice are discussed. A 47-item list of references is included, and three tables present study data. (Author/SLD)