I was wondering if anyone would mention that story in the comments. I definitely agree that it has very strong similarities in its core idea, and wondered if that was deliberate. I don't agree with any implications (which you may or may not have intended) that it's so derivative as to make not mentioning Omelas dishonest, though, and independent invention seems completely plausible to me.
Edited to add: although the similar title does incline rather strongly to Omelas being an acknowledged source.
Interesting re-write of Ursula K Legion’s ‘The Ones Who Walk Away from Omelas’