effect of comparable magnitude can
be ruled out in science. The nine
school systems for which we can rule
out large-scale class-size effects in
both mathematics and science are the
two Belgian schools, Canada, the
Czech Republic, Korea, Portugal,
Romania, Slovenia, and Spain.
Finally, we can rule out any
noteworthy causal effect of class size
on student performance in two
countries, Japan and Singapore.Did you follow that? After sorting
through thousands of pages of data on
student performance from eighteen
separate countries, the economists