The website, Lawschoolnumbers.com, has aggregated some statistics on the attrition rates among 1L at the nation's top 200 law schools.  In their report, Santa Clara ranks 33rd in the list, with 16.9% of 1Ls not continuing into their second year. 

1L Attrition Rates -- Lawschoolnumbers.com

(h/t to law librarian blog)