This is a very entertaining talk by one of the eminent researchers of positive psychology, Dan Gilbert. He moves quickly, so a teacher might want to stop and highlight some of the experiments more slowly, but overall, he's very engaging. He describes experimental research on not-so-intuitive ideas about happiness.
Students can take a test here to analyze their own strengths. Happiness research shows that knowing our strengths can help us be positive, so teachers can also share that piece of research with their students.
There is an entire MOOC offered for free for teachers to help them learn how to incorporate positive psychology in the classroom. This MOOC includes the research behind teaching character, as well as help creating a plan to incorporate positive psychology into the classroom.