Let me continue the example...
We found that students participating in the "2hr active recess program" have meaningfully better health outcomes, psychological health outcomes, and better grades. It was tested faithfully in 25 schools over 10 years.
It expands to other places. Different countries. Different decades. Different people run it in different ways. The kids are different. In some cases, the kids are already so active that the extra activity is detrimental. In some places, it's really hot. Kids tend to read, or do more organized indoor activities.
Basically, the world is not a laboratory. You're not predicting the trajectory of a projectile, where unknowables can be quantified as a function. It's all 3 body problems all the time.
Yet, we as humans do manage to make sense of the world. We run schools, companies. We learn more about how to do those things. Formal studies are an important part of learning about how to do those things. Scientific mindset and methodologies are useful to this. It's a lot better than just philosophizing the whole thing. The type of knowledge we gain, OTOH, isn't like F=MA. It never will be.
The value of the above study does relate/imply to it containing knowledge. It's a partial knowledge of a general problem. It is not complete knowledge of a particular problem, like you would get in a lab. Neither lab experiments or wild studies tend to replicate in one another's world.
No matter how good the study, how many times it replicated, or how well it worked throughout the 80s and 90s... there's no guarantee that your program is working well or a guaranteed explanation for why it isn't.