A retake is a second attempt to achieve a desired outcome. In the context of exams, it refers to retaking an examination after failing or not meeting expectations on the first try.
I liked the idea of retaking control over my career and the insurance that belonging to a group like Book View Cafe would bring. (publishingperspectives.com)
In Virginia, school accreditation ratings are based on students meeting achievement standards on tests in English, history / social science, mathematics, and science (with possible adjustments for ELL and transfer students and for preparing students for retakes of the state tests). (ascd.org)