Self-service design tools are flooding K-12 environments and altering the way instruction can be designed and delivered. As a result, schools are utilizing existing academics to both design and teach their own curriculum. These academics, called "designers-by-assignment", tend to have limited training in instructional systems design and instructional design theories. An overarching research question guided this study: How do K-12 designers-by-assignment use self-service instructional design tools to develop courses? A multiple-case study design included seven participants who taught K-12 music, designed and implemented curriculum using interactive whiteboards, and did not have instructional design experience or training. Qualitative data sources included a recruitment checklist, interview guide, artifacts, an observation guide, and a think-aloud protocol. Digital recordings from interviews and observations were transcribed and member-checked then coded, triangulated, and presented according to participants' technological knowledge, pedagogical knowledge, and content knowledge. A cross-case analysis suggested this sample of designers-by-assignment focused on pedagogy over technology to drive design decisions, self-service design tools loosely resembled traditional teacher-oriented instructional design models, and roughly half of the participants had transitioned to student-centered classrooms as their learning designs clearly privileged learners. The core technological belief for all seven designers-by-assignment was an overwhelming unpreparedness during pre-service education courses, and although the sample lacked knowledge of evidence-based multimedia design principles, several principles had still been implemented through a trial-and-error process. However, participants failed to identify how the principles contained sound instructional design theory, further confirming that key instructional design practices and theories are missing in a designers-by-assignment's knowledge base. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]