The chapter discusses the evolution of educational goals from a focus on cognitive outcomes to a broader concern with social and affective aspects, particularly the reemphasis on noncognitive outcomes like self-concept. It highlights the increasing number of studies on self-concept and the importance of enhancing children's self-concept, especially in programs for disadvantaged students. The authors critique the current state of self-concept research, noting that definitions are imprecise and measurements are not always equivalent, leading to difficulties in interpreting results. They propose a constructive approach to defining self-concept, emphasizing its multifaceted, hierarchical, stable, developmental, evaluative, and differentiable nature. The chapter also outlines methods for validating self-concept interpretations, including logical analyses, correlational techniques, and experimental studies. Finally, it reviews the validity of five widely used self-concept instruments, providing detailed critiques and suggestions for further research.The chapter discusses the evolution of educational goals from a focus on cognitive outcomes to a broader concern with social and affective aspects, particularly the reemphasis on noncognitive outcomes like self-concept. It highlights the increasing number of studies on self-concept and the importance of enhancing children's self-concept, especially in programs for disadvantaged students. The authors critique the current state of self-concept research, noting that definitions are imprecise and measurements are not always equivalent, leading to difficulties in interpreting results. They propose a constructive approach to defining self-concept, emphasizing its multifaceted, hierarchical, stable, developmental, evaluative, and differentiable nature. The chapter also outlines methods for validating self-concept interpretations, including logical analyses, correlational techniques, and experimental studies. Finally, it reviews the validity of five widely used self-concept instruments, providing detailed critiques and suggestions for further research.