Educational Robotics has gained popularity in K-12 education as an effective tool to teach STEM topics and skills like computational thinking, programming, collaboration, and creativity. With rapid technological progress, educational robots have found ways into classrooms worldwide. However, challenges like the ease of use, cost, and requiring specialized skills to operate and teach using these tools have hindered widespread adoption. In this dissertation, I present "Smart Motors," a trainable educational robotics system, as a solution to these accessibility issues. By shifting from programming strategy to training, "Smart Motors" eliminates the need for computers and the internet to produce desired outcomes. Iterating through a series of improvements in design and components, we built a trainable robotics kit under $30. "Smart Motors" were used in several workshops and classrooms in different countries, and the results show that they can be integrated into STEM classrooms with students from second grade to high school. I present three proof of concept studies using three "Smart Motors" prototypes with different age groups in different settings from engineering design and arts to science investigation in order to show "Smart Motors" effectively fulfills the learning objectives. The usability tests on one of the prototypes with 7 to 15-year-old participants showed how they could discover the training features independently. It also showed that "Smart Motors" are highly likable and capable of producing diverse solutions quickly. Investigation of playful learning experience characteristics, while engaging in a play-based activity with "Smart Motors," revealed that "Smart Motors" supports playful learning. Through collaboration with partners in the US, Brazil, and Nepal, we have created "Smart Motors" resources for teachers to introduce educational robotics in their STEM classrooms. [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.]