e></p></dd>

<dt>grade</dt>
<dd><p>grade in school</p></dd>

<dt>age</dt>
<dd><p>student age</p></dd>

<dt>race</dt>
<dd><p>a factor with levels
<code>other</code> <code>White</code></p></dd>

<dt>urban.rural</dt>
<dd><p>a factor with levels
<code>Rural</code> <code>Suburban</code> <code>Urban</code></p></dd>

<dt>school</dt>
<dd><p>a factor
with levels <code>Brentwood Elementary</code> <code>Brentwood Middle</code> <code>Brown
Middle</code> <code>Elm</code> <code>Main</code> <code>Portage</code> <code>Ridg