With social-emotional learning's (SEL) significant impact on academic, emotional, behavioral, social, and lifelong success, it is necessary to ensure its continued adoption, implementation, and effectiveness within schools. While SEL is at its highest levels of awareness and implementation, it still faces significant barriers to effectiveness. Despite every state implementing aspects of SEL and 46 states having adopted SEL-related standards, only 24% of schools use effective SEL assessments. It is difficult to accurately evaluate SEL growth and program effectiveness without well-designed valid, and reliable SEL-based assessments (e.g., diagnostic, formative, summative, progress monitoring, and standards-based). The vast majority of SEL assessment tools are not aligned with widely accepted frameworks such as the Collaborative for Academic, Social, and Emotional Learning (CASEL) 5-component model. These assessments also suffer from several other failings: (1) not aligned with SEL standards, (2) lacking multiple reporter formats, (3) missing formative information for progress monitoring, (4) unable to deliver timely results and interpretations, and (5) fail to affect SEL development that could be available with digit assessment and intervention tools. This research found that only three tools met a majority of these criteria, none meeting all criteria. To further the development and implementation of SEL assessment instruments, the Social-Emotional Learning Digital Diagnostic Assessment (SELDDA) tool was studied to determine its impact on educator social-emotional learning development. Through quantitative analysis of reliability, validity, and usability, this study evaluated the SELDDA assessment. [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.]