s estimating the effects of modified school calendars on students’
achievement. The 56 studies were run in individual schools, which can be
grouped into 11 districts. We might expect more similar effect size
estimates from schools in the same district – in other words, the effect
size estimates from the same district might not be completely
independent. Consequently, we might want to adjust for this dependency
(clustering) between the effect size estimates to draw a more
appropriate inference.</p>
<p>Fi