Grade retention or grade repetition is the process of a student repeating a grade after failing the previous year.

In the United States, grade retention can be used in kindergarten through to third grade; however, students in high school are usually only retained in the specific failed subject. For example, a student can be promoted in a math class but retained in an English class. Most elementary school grades (kindergarten through 5th grade) are taught all subjects in one classroom for the whole day, with exceptions in art and athletics. In these grades, the student who fails or scores below the accepted level in most or all subjects is to be considered for retention. If ultimately retained, the student will then repeat the entire school year's curriculum.

Where it is permitted, grade retention is most common among at-risk students in early elementary school. At-risk students with intellectual disabilities are only intended to be retained when parents and school officials agree to do so. Children who are relatively young in their age cohort are four times more likely to be retained.

Mandatory grade retention of third-grade students who struggle in reading has been a critical part of the Mississippi Miracle, which has seen several low-performing states soar in the national rankings as their students demonstrate increased confidence and capabilities in both reading and mathematics.

Different schools have used different approaches throughout history. Grade retention or repetition was essentially meaningless in the one-room schoolhouses of more than a century ago due to limited access to outside standards and the small scale of the school with only a few students in each age group, was conducive to individualized instruction. With the proliferation of larger, graded schools in the middle of the nineteenth century, retention became a common practice and only one century ago, about half of all American students were retained at least once before the age of thirteen.

An alternative to grade retention due to failure is a policy of social promotion, with the idea that staying within their same age group is important. Social promotion is the obligatory advancement of all students regardless of achievements and absences. Social promotion is used more in countries which use tracking to group students according to academic ability. Some academic scholars believe that underperformance must be addressed with intensive remedial help, such as summer school or after-school programs in contrast to failing and retaining the student. Social promotion began to spread in the 1930s with concerns about the psychosocial effects of retention. Social promotion is the promoting of underperforming students under the ideological principle that staying with their same age peers is important to success. This trend reversed in the 1980s as concerns about slipping academic standards rose, and the practice of grade retention in the United States has been climbing steadily ever since. However, in most other countries, retention rates have been decreasing.

The practice of making retention decisions on the basis of the results of a single test, called high-stakes testing, is widely condemned by professional educators and test authors alike. Indeed, Mississippi and other states use data points from multiple tests to determine if a child is to be retained or not.

Academic studies on grade retention are difficult to perform and analyze for several reasons. However, the empirical benefits of grade retention have been clearly demonstrated.