Pay It Forward (2000)

School teacher Eugene Simonet (Kevin Spacey) sets his class an assignment: they must each think up a way to make the world a better place. This prompts eleven-year-old Trevor McKinney (Haley Joel Osment) to develop the idea that instead of paying back good deeds, one should instead pay them forward. Putting his idea into practice, Trevor performs an act of kindness for three different people, requiring each of those three to perform three further kindnesses themselves. In doing so he starts a chain reaction which does indeed make the world a better place.