This document summarizes a study on lessons in happiness taught to secondary school students in the Netherlands. It provided an overview of the study which randomly assigned 15 classes (381 students) to receive 6 lessons on happiness over 50 minutes each, while a control group of 10 classes (250 students) received the usual mentor classes. Questionnaires were given before and after to measure happiness and health, and grade point averages were compared before and after. The results showed that students who received the happiness lessons had higher GPAs at the end of the school year compared to the control group.