||The title of this article is a conjecture.
Though the topic is found within The Simpsons universe, a proper name is not available.
The 5th grader is a member of the 5th grade at Springfield Elementary School.
After Bart hit him to get him out in Dodgeball, he caught the ball meaning that the 4th Grade lost the game. This started a war in the school between the 4th grade and the 5th grade. Eventually, Bart realized that he had the same sword scar on his hand.
Bart found out that Marge used to be a member of a group called The Cool Moms. They would take their children on play dates and the 5th Grader was one of them. As Marge and the other moms got back together, so did their children. The 5th Grader and the other kids dared Bart to do crazy things and Bart wanted to split them up again, which they eventually did.