Artificially concentrating smart kids in a group and then scattering them into the world is pretty counterproductive. I mean, it makes the school district look good ("We have 120 high-IQ students in the county! Stellar exam scores! We're fantastic!"), and at the end of the day, that's all the matters. The school system doesn't care much what happens after the students have left it.
For academic achievement, the majority of research backs up your thesis, and it isn't even a tradeoff, where you get better academics at the expense of worse socialization. Gifted programs don't work. It is far better to accelerate a student to a higher grade, even if it means putting students in classes with much older students (accelerating a gifted student is the most effective positive intervention that can be taken in K-12 education according to Hattie's recent review of meta-analyses, Visible Learning, and nothing else is close). It pushes them academically, and more often than not, helps them socialize, because they learn how older kids interact before internalizing too many abnormal frames and social habits.
So maybe we have to work with what we've got - 14yo that can learn fast - so teach them fast. Can't do it in the regular classroom, so gifted class. Socialization is apparently an issue there (why? same age group as other kids have, same teacher - what's really different?) so work on that.
I was also in a G+T program in the 80s and I'd say a major problem in young adult years is no one cares how smart you are, after 16 or so years of being told there's nothing more important than being smart. Much like your GPA, your IQ is pretty much irrelevant once you graduate. Workplace progress suddenly switches entirely over to who you know, who is your dad, who you impress, who you kiss up to, your golf game, etc.