The Multi-State Professional Responsibility Exam (MPRE) is a requirement for admission to practice law in all but a few states.  The MPRE is a half day, multiple choice exam that tests your knowledge of legal ethics rules.  The MPRE is not a part of the Bar Exam but you cannot become licensed without passing.  Your law school will likely teach a course on legal ethics rules that acts as a precursor to the exam itself. 
    You can take the exam your second or third year; most students take the exam the third year.  The scores required to practice in the various states is listed at the BarBri site ( and in the BAR/BRI Digest.  The BarBri site and the Digest indicate if the state where you are going to take the Bar Exam requires the MPRE.  Again, consult your state’s Board of Law Examiners for the final say on the MPRE requirement.