Point Roberts, Washington, is the tip of a peninsula that hangs a few miles below the 49th parallel, so when the border was ruled straight across the map it came out American and cut off, by land, from the rest of America. The town’s own school is small, so older children ride a bus north into Canada, along through the suburbs, and back south into the United States to reach school in Blaine: two international borders before first period, two more on the way home. Most people cross a border on holiday, with a passport and a little ceremony. These children cross it with homework, and probably have a better idea than any of us where it actually is.