SOLVED. story that contains a scene where a rat comes out of a swimming pool drain...[s]

[Tracie]

I can't remember which year I was in school, but a teacher read this to our class. It would have been in the 70's, it was set in an innner city, and the scene that stands out is one of the characters is swimming in a pool (YMCA?) and a rat swims out of the drain and attacks the boy.

???

[Tab]

Mystery of the Fat Cat could be it.

Here's a review from Kirkus:
Kids will flip over this one--it's funny, original, funny, enterprising, FUNNY, entertainment and if you look, closely, makes a couple of more serious points. It's about Buddy Williams, a kind of slow-moving boy with a sometime stammer and some of his friends--all origins--and their Boys Club in Dogtown. The club's about to be closed down when a rat in the drain of the swimming pool bites Buddy. (view spoiler)[Some adults will be closing down on this one after Mr. Hannibal, head of the Boys Club, says he'd rather his boys smoked pot than cigarettes since it ""doesn't crud up your lungs."" Anyway, the Boys Club has a chance, since it will inherit a great deal of money, $639,943,96, once the natural heir--a tomcat Buzzer Atkins--dies. He's in the care of a man called Shriker who seems to have extended his life eternally. Anyway Buddy suspects that Buzzer is not 28 years immortal, takes a picture from the library microfilm of the original, prompts an escape by releasing his replacement, digs up the box with the remains of not-so-old Buzzer Atkins, and is guilty of charges of trespassing and harassment. . . . (hide spoiler)] Fat Cat's got lots of whiskers and the biggest smile in many a mystery.

[Tracie]

That sounds like it! Thanks so much! This group is amazing!