So it's a 4th vs 54th grade dodgeball tournament at school and Bart wins, but due to a technicality, whih unleashes a 4th-vs-5h grade war. The war spreads to the teacher lounge, which turns into a saloon bar-fight (even with Skinner playing the piano). Soon they decide to ends it with a fight, but in it, Bart and a 5th grader guy (who we'll call Otis) discover they have the same scar in their hand (which we never saw before).
Bart soon tells Marge about his scar and Marge revelas how she was a member of a group called The Cool Moms and reunites the group. Homer has to hang out with the lame boring agressive husbands and Bart with the violence loving kids. Bart soon starts to dislike the meetings, and decides to find a way to disband the group again.
He is sure the scar they have is the source of the initial fallout, so they go to COmic Book Guy who was there in the incident. On 4th of July yhears ago, everyone was at the fireworks show, and Bart, Otis & the 2 kids deicde to unleash all fireworks at once. The chaos burns CBG's sandwich, and the sowrd toothpicks fall on the kids hands.
Bart then tries to make another fireworks chaos and Marge discovers him. He tells the mom about it and they go and insult Bart, so Marge leaves the group. Then the moms start to kiss each other.
Overall: This episode was pretty good. It has an interesitng story & good jokes (Flanders' moustache, Marge's brain..) so 8.5/10.