Question: What episode was the "The Kids are all Fight" when The Simpsons aired its twenty-sixth season on Fox?

Context paragraphs:
Mathlete's Feat: "Mathlete's Feat" is the twenty-second episode and season finale of the twenty-sixth season of the American animated sitcom "The Simpsons", and the 574th overall episode of the series.  It originally aired on the Fox network in the United States on May 17, 2015.

The Kids Are All Fight: "The Kids Are All Fight" is the nineteenth episode of the twenty-sixth season of the American animated sitcom "The Simpsons", and the 571st overall episode of the series.  It originally aired on the Fox network in the United States on April 26, 2015.

Clown in the Dumps: "Clown in the Dumps" is the season premiere of the twenty-sixth season of the American animated television series "The Simpsons", and the 553rd episode of the series overall.  It first aired in the United States on the Fox network on September 28, 2014, with "The Simpsons Guy", a crossover episode of "Family Guy" with "The Simpsons", airing afterwards.  This episode was dedicated in memory of Louis Castellaneta, the father of "The Simpsons" voice actor Dan Castellaneta.  It was written by Joel H. Cohen and directed by Steven Dean Moore, with Don Hertzfeldt directing a sequence in the opening titles.  Jeff Ross, Sarah Silverman and David Hyde Pierce guest starred as themselves, with Jackie Mason and Kelsey Grammer reprising their respective roles as Rabbi Krustofski and Sideshow Bob, while Maurice LaMarche voiced several minor characters.

Peeping Mom: "Peeping Mom" is the eighteenth episode of the twenty-sixth season of the American animated sitcom "The Simpsons", and the 570th overall episode of the series.  It originally aired on the Fox network in the United States on April 19, 2015.

The Simpsons (season 26): "The Simpsons"' twenty-sixth season premiered on Fox in the United States on September 28, 2014 and concluded on May 17, 2015.

Bull-E: "Bull-E" is the twenty-first episode of the twenty-sixth season of the American animated sitcom "The Simpsons", and the 573rd overall episode of the series.  It originally aired on the Fox network in the United States on May 10, 2015.

Waiting for Duffman: "Waiting for Duffman" is the seventeenth episode of the twenty-sixth season of the American animated sitcom "The Simpsons", and the 569th overall episode of the series.  It originally aired on the Fox network in the United States on March 15, 2015.  R. Lee Ermey reprises his role of Colonel Leslie Hapablap from "Sideshow Bob's Last Gleaming".  The title is a play on "Waiting for Guffman".

The Princess Guide: "The Princess Guide" is the fifteenth episode of the twenty-sixth season of the American animated sitcom "The Simpsons", and the 567th overall episode of the series.  It originally aired on the Fox network in the United States on March 1, 2015.  The episode was dedicated to the memory of Leonard Nimoy, who died two days before the episode aired.  Nimoy guest-starred in two "Simpsons" episodes, "Marge vs. the Monorail" and "The Springfield Files".

Simpsorama: "Simpsorama" is the sixth episode of the twenty-sixth season of the animated television series "The Simpsons", and the 558th episode of the series overall.  It originally aired on the Fox network in the United States on November 9, 2014.  "Simpsorama" is a crossover with "Futurama", another animated series created by "The Simpsons" creator Matt Groening, that had previously aired on Fox and later Comedy Central before concluding in September 2013.

Let's Go Fly a Coot: "Let's Go Fly a Coot" is the twentieth episode of the twenty-sixth season of the American animated sitcom "The Simpsons", and the 572nd overall episode of the series.  It first aired on the Fox network in the United States on May 3, 2015.  The episode's title is a parody of the song "Let's Go Fly a Kite".

Supporting paragraphs: The Kids Are All Fight The Simpsons (season 26)
Answer: the nineteenth episode