There's nothing hindsight about this. We can make confident predictions: whatever this is, it will prove to be of very limited use or none at all. Why am I so confident? Because like with boosting IQ, researchers keep trying, and they keep failing. Their repeated failures tell us a lot about the probability the next study will succeed...

Education is full of big gains promoted to anyone who will listen as the answer to this or that gap - like this one! - which turn out to be flukes (p=0.05 means you just need to keep trying...), statistical or data gaming (what does it really mean to have some specially treated kids reclassified into the gifted program? are the people choosing for the gifted program even blinded as to which kids they are expected to choose and vindicate this expensive program?) and Goodhart's law, regression to the mean or 'fade out', and outright fraud.

like Head Start; there are benefits - and then they fade away: https://secure.wikimedia.org/wikipedia/en/wiki/Head_Start_Pr... or http://edlibertywatch.org/2011/03/studies-on-effectiveness-o... Suppose this study had been conducted in this http://www.ajc.com/news/investigation-into-aps-cheating-1001... recently exposed nest of crime?

You're addressing something different. I interpret the grandparent as "this study tells us what was intuitively obvious" which is hindsight bias.