Small, elite schools outside of major metro areas in the northeastern US are commonly characterized by a “work hard, play hard” culture that includes a party scene. This is not something unique to Lehigh; for example, if you take another look at the current Princeton Review party school list, you will see that two of Lehigh’s peer schools in the Patriot League, Bucknell and Colgate, are also highly ranked.
Note that partying is optional. There are plenty of non-partiers at these schools, and they simply socialize with other like-minded individuals. The administration at Lehigh, and probably at other schools, makes a deliberate effort to schedule alternative social events that are entertaining without intoxication.
If you want a small elite northeastern school with less partying, look at urban schools, schools with religious affiliations, liberal arts colleges that have banned frats, and former women’s colleges that have gone coed.