Research on the scarring effects of primary-grade retention has produced mixed results. Some studies have found that retained students experience a range of negative outcomes, including lower academic achievement, lower self-esteem, and increased dropout rates. Other studies have found that retention can have positive effects for some students, such as improved attendance and behavior.

The long-term effects of retention are still debated, but there is some evidence that it can have negative consequences for students' educational and social development. For example, a study by the National Center for Education Statistics found that retained students were less likely to graduate from high school and more likely to be unemployed as adults. Additionally, retained students may experience social stigma and isolation, which can further impact their academic success and well-being.

However, it is important to note that retention is not always harmful. In some cases, it can be a necessary step to help struggling students catch up academically. For example, a study by the University of Chicago found that students who were retained in kindergarten were more likely to be proficient in reading and math by the end of third grade.

Ultimately, the decision of whether or not to retain a student is complex and should be made on a case-by-case basis. There are a number of factors to consider, such as the student's academic progress, social and emotional development, and the availability of support services.