In this paper we describe our investigation of underrepresented high school students' interests, engagement, and experiences in design-based Information and Communications Technology (ICT) summer workshop activities; with the goal of identifying activities, aspects, and/or elements of the program that can be tailored or improved upon to attract, engage, educate, and retain high schoolers who have historically been underrepresented in ICT. Our primary research question is "which activities are most engaging for students typically underrepresented in ICT careers and programs," and we additionally report on underrepresented students' experiences and psychosocial changes across the summer workshops. A total of 139 high school students (of which 98 identified as being underrepresented female and/or racially minoritized students) participated in the ICT workshops hosted across three consecutive summers at a large, public, urban university in the Midwestern region of the United States. Employing a mixed methods design, our quantitative results and qualitative findings suggest that underrepresented students in our sample found the summer workshops' group projects and hands-on courses to be the most engaging activities. Implications of our results/findings are further discussed.