Answer:
The educational setback that occurs when students forget some of the information they learned during the school year is known as summer learning loss (also summer setback or summer slide).
Explanation:
When coming back to school after a long period of holidays, it is common for students to show loss of knowledge and academic skills. That fact can be measured by the use of a standardized test right before the holidays and again when students return to school. The loss varies according to different factors such as age, subject, and even family income. Still, in general, researchers have found that the loss of knowledge is greater in mathematics, and that students in higher grade levels tend to lose more than those of lower grade levels.
That's incorrect usage.
You'd say "I haven't seen him"
