Article: Graduate schools include the School of Medicine, currently ranked sixth in the nation, and the George Warren Brown School of Social Work, currently ranked first. The program in occupational therapy at Washington University currently occupies the first spot for the 2016 U.S. News & World Report rankings, and the program in physical therapy is ranked first as well. For the 2015 edition, the School of Law is ranked 18th and the Olin Business School is ranked 19th. Additionally, the Graduate School of Architecture and Urban Design was ranked ninth in the nation by the journal DesignIntelligence in its 2013 edition of "America's Best Architecture & Design Schools."

Now answer this question: Where did the School of Law rank in  2015 by the U.S. News & World Reports?
18th