The purpose of this phenomenological study was to examine how integrative STEM teachers utilize the "Standards for Technological and Engineering Literacy" (STEL) to foster and assess 21st-century learning in technology and engineering classes at multiple Virginia public secondary schools. The theory guiding this study was Kolb's experiential learning theory, which integrates nine learning theories into an innovative cyclical learning process that is like the engineering design loop. This hermeneutic phenomenology included 15 Virginia technology and engineering schoolteachers (Grades 6-12) who purposefully taught multiple academic disciplines and utilized the eight practices of the STEL in the context of their curriculum to foster 21st-century learning. Data collection included individual interviews, journal prompts, and physical artifacts (lesson plans, assessment tools, etc.). Data were entered into the Delve data analysis software and were analyzed using Van Manen's hermeneutic phenomenological theory for common themes regarding the fostering and assessment of 21st-century literacy. The themes extracted from the data included measuring 21st-century learning, developing 21st-century curriculum, and the eight practices of technology and engineering educators: creativity, collaboration, communication, critical thinking, optimism, attention to ethics, systems thinking, and making and doing. The findings indicated that integrative STEM methodology, multidisciplinary instruction, and the eight practices of the STEL fostered 21st-century learning. This study's significance was to add to the available literature on integrative STEM education and the STEL fostering 21st-century learning. [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.]