What is good for a society and what feels just are often disparate things.
But it is not unjust on a human scale that some people are born with lower potential than others. It’s just an unfortunate fact of life.
What is just then?
To whom is it just to invest 2x the resources into a person that will never likely tinder a significant benefit to society?
To whom is it just to -not- invest in people who are particularly likely to bring benefits to society?
We know that the vast majority of significant advances in engineering and science are brought to life by people that are significantly above average capability in their fundamental capabilities, gifts that were evident even before they entered school.
We know that significant advances are unlikely to be contributed by people for whom day to day life is a significant cognitive challenge.
This comes down to the harm / benefit of investing 2x the effort into one person.
The best likely case scenario for the bright student is that they go on to create something remarkable and useful. Advancements in technology and science are responsible for millions of lives saved every year, and billions of lives saving trillions of man hours they would have spent in tedious, exhausting work. This then translates into higher investment in children, creating a virtuous cycle of benefit.
The best likely case for the dim bulb is not so different than the no-intervention path, but with a slightly better quality of life. The best argument is probably that it might make a difference in how he approaches parental responsibilities, since his social crowd is likely to be of slightly better character.
I would say it is unjust to the many to focus your resources on the least productive in society, unless the reason for their lower potentiality is something that is inherently fixable (IE lack of education). If the problem is endemic to the individual themselves, it makes little difference or sense to invest a disproportionate effort in their education.
OTOH if you have a student that can absorb information at double or triple the normal rate, it makes sense to fast track them to a level of education that they can produce benefits to their society. To let them languish in a classroom developing a disdain for their teachers, whom the often know more than, only creates habits and preconceptions that guide them into dubious but interesting activities and away from the paths that might lead them to greatly benefit society at large.
Either way it’s kind of a shit sandwich though, so who knows.
Anecdotally for me, G/T was great for my eventual development, and probably moved me farther away from a life of high achieving white collar crime, which seemed like a worthwhile goal when I was 9.
Showing me that other people understood and valued my intellect was a huge factor in deciding to try to do something admirable with my life.
It also was largely a waste of money paying for me to launch mice to half a mile in spectacularly unsafe sounding rockets from the school track. The astronaut survival rate was not great.