In this work the authors investigate the effectiveness of robotics in education. Rather than creating excitement for children when playing with robots in games, they are examining the overall learning environment where a robot acts as a teaching assistant. They designed a suitable lesson plan when groups of teenagers participate in activities involving the use of the robot: the authors first performed experiments for the robot to solve the "Tower of Hanoi" problem; then, they designed a lesson plan to teach the "Tower of Hanoi" problem using a KUKA youBot as a teaching assistant. The experiment involved two groups of students: one group was taught with the robot and the other group without the robot. Finally, the authors present results of a comparative study based on questionnaires, in order to understand if the effectiveness of the teaching has been greater with the robot as teaching assistant.