In this study, we designed and evaluated the effectiveness of a new course aimed at developing creativity as the cornerstone of technology and design education. This 14-hour synchronous online course was offered to secondary school students in the online format by the Open Educational Laboratory by the National Center of the Junior Academy of Sciences of Ukraine. Forty-three students completed the course consisting of online class sessions, presentations, recommended books, articles and videos, and homework for independent study. Pre- and post- divergent thinking tasks were used to assess how the course influenced design and creativity outcomes. Additionally, we evaluated the relationship between course effectiveness and participants' behavioral engagement level as well as domain of participant's and interest. The findings revealed that divergent thinking may in fact be fostered within an online course aimed at exploring possible sources for ideas, yet without a direct focus on divergent thinking tasks as such. After training, participants were able to generate significantly more varying and creative ideas than before training. However, positive changes in originality and usefulness of participants' ideas were not observed. During the planning of further trainings, it is worth supporting participants' articulation and reflection on the usefulness of their ideas. A positive relationship was identified between student activity during class sessions and development of their creativity. An important implication from this study is that encouraging students during the course and provision of regular feedback from the instructor make a measurable difference in creativity outcomes.