Assessments have become somewhat common in BigLaw recruiting. Assessments typically take the form of behavioral surveys created by third-party companies in conjunction with the firm. Then, law firms can use this information as an additional factor in hiring decisions.
Many law firms use assessments as a supplement to traditional factors (resume, transcripts, interviews, etc) with the purpose of making better hiring decisions and expanding the breadth and diversity of their summer classes.
Law students may have mixed feelings about assessments. However, it can be a required part of the recruiting process for some firms and important for law students to understand!