"Is there any non-theoretical reason to believe KIPP doesn't work? I.e., do KIPP students underperform in some way?"
There isn't enough data to say.
"But without delving into theory, you can certainly tell me what the measurable effect will be."
Cognitively, I'd be most concerned about whether the program would be harming their executive function and their intrinsic motivation. I don't see any value of trying to predict specific metrics though, beyond identifying specific metrics to look at once more data exists.
I'd also worry that such a program might reduce the ability of kids to function independently and instead reinforce the ideas that large government institutions should displace the family as a means of childrearing.
There isn't enough data to say.
"But without delving into theory, you can certainly tell me what the measurable effect will be."
Cognitively, I'd be most concerned about whether the program would be harming their executive function and their intrinsic motivation. I don't see any value of trying to predict specific metrics though, beyond identifying specific metrics to look at once more data exists.