The prime minister ran around a balmy ball hockey court at the leafy 147-year-old institution, the Bishop Cotton Boys' School.
Hundreds of students and sari-wearing teachers pressed up against a chain link fence to watch the Canadian leader take a few whacks at the ball.
Harper played with a group of teenage girls from an adjoining school, while junior sport minister Bal Gosal played with the boys.
Earlier, Harper had gotten some tips on playing cricket from the school's cricket team.
This was Harper's last stop on a six-day tour of India, before heading to the Philippines and Hong Kong.