That's the old-fashioned alternative to "accelerated" classes and "tracking" for the "gifted." It's making a comeback.
There's some real justice to it. If you can do more work earlier, aren't you entitled to finish the task -- in this case, high school -- earlier? Why should you be burdened with additional work? It's like what I hate most about a 9 to 5 job: You don't get off early for getting a lot done.
I remember when grade-skipping went out of fashion. It was right around the time when I was in grade school. My mother told me later that they wanted me to skip, and she was adamantly against it. I was outraged that I wasn't asked and that I was stuck with a whole extra year of sitting in a classroom. She knew better. She had been skipped back in the old days, during the Depression. (She went to college at 16.) Based on her experience, she felt sure she knew skipping was bad.
Now, I know I wouldn't exist if she hadn't been skipped! She would not have graduated from college when she did and gone on to the situation in which she met my father. But you can't make a list of all the things that set the stage for your conception and count them as good. This is especially clear in my case: My parents met in the Army in WWII. Still, I regretted not skipping! The whole explanation was a social one, as if life will be so wonderful if only you're surrounded by kids your own age.
So now, some experts are saying go ahead and skip kids again.
It is stunningly efficient. You don't have to set up special classes for the quicker students, and the students themselves have their time saved. And I like that idea that these students are just going faster, replacing the idea that they are gifted, belonging in a separate room, on a separate track. "Gifted" sounds preening and even rather religious. It sounds as though there's something wrong with giving the student credit for achievement.
Getting to go faster because you're actually getting the work done faster has a more egalitarian feel to it. All kids can understand the concept, which is similar to the idea that if you finish your homework an hour early, you can do whatever you want for an hour. It's a nice incentive. Imagine if kids were told: If you finish your homework an hour early, we'll give you an extra hour's worth of homework. So letting the quick kids finish early ought to inspire the other kids to try to get their work done fast. Wouldn't that be better than for them to see those kids given harder work?
UPDATE: Lawprof Tung Yin, who did skip, says maybe it's different for boys. He notes that he was originally one of the younger kids in his class so he was really young after the skip. That was also true of my mother, and one of the reasons I was especially upset with her judgment was that I was always one of the oldest kids. I would have just taken a normal place among the youngest unskipped kids, which probably would have been a nice advantage for a girl.