d by school district, by school, by classroom, and by demographic features of the individual students or the school as a whole. Depending on the variables of interest, different structured subsets should be evaluated. For example, the focus of interest may be on the performance of entire classrooms, so it would make sense to cross-validate at the class or school level on classroom performance.</p>
</section>
<section id="cross-validation-with-spatio-temporal-data" class="level3 unnumbered">
<h3 class="unnum