one size fits all

Supposedly well-suited to any situation, as of a product, method, solution, etc. Often hyphenated. A: "Hey, maybe this shirt would fit you—it's one size fits all." B: "I doubt it—when you're 6'6" like me, 'one size fits all' never applies." I know you've had success in other school districts, but a one-size-fits-all approach isn't going to work here. You need to come up with something more personalized, something that gets the townspeople to trust you.