David and Goliath: Underdogs, Misfits, and the Art of Battling Giants

the same teachers, the same principal,
the same textbooks. It was in the same
building in the same town. The local
economy and the local population were
virtually identical. The only thing that
changed was the number of students in
fifth grade. If the students in the year
with a larger enrollment did better than
the students in the year with a smaller
one, then we can be pretty sure that it
was because of the size of the class,
right?
This is what is called a “natural
experiment.” Sometimes scientists set up
formal experiments to try and test
hypotheses. But on rare occasions the
real world provides a natural way of
testing the same theory—and natural