This paper considers a science lesson given through mediation of the humanoid RoboThespian to groups of school students (grades 5-7) at the science museum MadaTech. The lesson included theoretical explanations, hands-on experiments, and a knowledge quiz, all instructed and managed by means of the robot-teacher through programmed behaviors and remote teleoperation. We report the lesson design, implementation, and students' outcomes in two different classroom settings. The connection among the student-robot interaction, the learning outcomes, and the class characteristics is discussed.