I'm not super familiar with the actual usage of this term. There is a short Wikipedia entry explaining that it's an educational approach that is being compared to the concept of forcing vegetables to mature quickly.
We place a high value on achievement for bright kids. We frequently do so at the expense of their welfare.
Placing younger kids in with older ones frequently gets them picked on and may get them sexually assaulted. This isn't really an approach that fosters a healthy, thriving society.
Real education teaches people to think for themselves and function as a citizen. Training teaches you how to work, not how to think, and in the information economy, we increasingly treat college like job training and this is a problem.
I declined my National Merit Scholarship. I allowed my son to decline college at age thirteen though he had been accepted.
I think we do this garbage because of heternormative culture and the red queen effect it fosters where everyone needs to run faster. But it's worse than that because aren't even staying in the same place. We are losing ground in important ways.
I write about a lot of topics and blogs like Eclogiselle and Project SRO are aimed at trying to put brakes on this red queen effect and the poverty and problems it causes. You don't remedy them by desperately trying to force kids with potential to learn things in short supply so they can be used as a tool with no real regard for their welfare.
I taught my sons that they needed to learn to feed their hungry minds in a fashion that was healthy. I'm sure Hitler was also bright. Some things, we don't desperately need more of, no.