This dissertation aims to bridge the gap between validity theory and the practice of validation. The dissertation employs a three-article approach. Following the introduction in Chapter I, three independent manuscripts representing three empirical studies are presented (i.e., Chapters II - IV). Each chapter is a stand-alone publishable manuscript, consisting of an introduction, review of literature, methods, results or findings, and discussion and implications. The Chapter II study used the Delphi method to explore measurement experts' conceptions of validity and validation. The purpose of the study was to define and reify three key aspects of validity and validation, namely test-score interpretation, test-score use, and the claims supporting interpretation and use. Definitions were developed through multiple iterations of data collection and analysis. By clarifying the language used when conducting validation, validation may be more accessible to a broader audience, including but not limited to test developers, test users, and test consumers. The Chapter III study used a phenomenological research design to explore K-12 teachers' perceptions of compassion and compassionate leadership. The purpose of this study was to conceptualize and operationalize compassionate leadership from the perspective of K-12 teachers. Data were collected through semi-structured interviews and analyzed using thematic analysis. Study findings highlight how social interaction, supportive relationships, and workplace culture mediate compassion and compassionate leadership in the context of K-12 education. The Chapter IV validation study used a quantitative approach to examine the Compassionate Leader Behavioral Index for Educators (CLBI-E); an instrument designed to measure compassionate leadership in PreK-12 education. CLBI-E development is described in the Chapter IV study, and Rasch (1960) measurement was used to evaluate validity claims related to the psychometric properties of the CLBI-E. A total of 68 PreK-12 teachers participated in this study. Results suggested the CLBI-E possesses strong psychometric properties; thus, presenting validity evidence based on the internal structure of the instrument. In addition to each Chapter's unique contributions to a respective field of study, Chapter V of the dissertation details how the studies presented in Chapter II, Chapter III, and Chapter IV work together to conceptualize validity and validation in educational and psychological testing. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]