<p>I think the main reason for ranking the publics lower is selectivity which is an important criterion. But, if publics became more selective to boost their rankings, they would loose sight of their mission.</p>
<p>^^ depends on the public school, but it seems to me that in the US News ranking, public schools are docked in areas like alumni giving, faculty resources, etc. which really causes them to be ranked lower. Berkeley, for example, is ranked #13 in selectivity; others, like UCLA and Michigan, are ranked in the top 20 for selectivity.</p>