The Effect of Grading Policies Used for Second-Chance Testing on Student Achievement in an Introductory Biology Course

In order to address underperformance and low retention in a majors introductory biology course, we implemented second-chance testing, hypothesizing that it would lead to an increase in exam grades. We divided the course content into 16 learning outcomes (LOs). Students tested over 3–4 LOs at a time during in-class exam days and had the option to retest on a limited number of LOs during in-class retake days. We implemented two different grading policies over two fall semesters. In one iteration we used a full replacement + insurance policy (i.e., Policy 1) in which only the highest grade for each LO exam was counted. In the second iteration, the exam score was calculated by weighting the lowest attempt at 25% and the highest attempt at 75% (i.e., Policy 2). Analysis of first-attempt and retake exam grades showed that students increased their LO exam average by ~14% through the use of second-chance testing under both grading policies. Students retested more often under Policy 1 and students earning ≥ 90% on a first-attempt LO exam retested only under Policy 1. Students earning < 70% on a first-attempt LO exam were more likely to retest under both policies compared with students earning a passing grade. A majority of students earning < 60% on a first-attempt exam were unable to achieve a passing grade for that LO through retesting, regardless of policy. Our data support the conclusion that second-chance testing can be used by students to make significant grade improvements and is especially important for students earning a D on a first-attempt exam. When using a modular approach in which many smaller exams are used, we recommend a full replacement + insurance grading policy due to higher rates of participation.