Or even a college which the average distance between any two people is 2 - 3 degrees. Additionally, this story is written from the perspective of Harry Potter so weaker ties won't be included as it doesn't advance the story.

Source: https://www.facebook.com/notes/facebook-data-team/anatomy-of... -- "When we limit our analysis to a single country, be it the US, Sweden, Italy, or any other, we find that the world gets even smaller, and most pairs of people are only separated by 3 degrees"