> Gifted children will get the stimulus they need at home via independent study or from their family.
Or by disrupting the rest of the class.
> Splitting gifted kids apart can warp them socially for life too.
Single streaming gifted kids can also warp them socially. Gifted kids in a single stream classroom need to learn to play dumb or become a social pariah. My school district had tracked 1-6, and semi-tracked 7-12. It was a real adjustment leaving the core group where learning and knowledge was appreciated and developed, even if most of the kids in the 'honors/advanced' sections were people I knew from the tracked grade school experience. My child had pullout 'branches' in his current school district 2-4, and AFAIK, it seemed pretty useless; my spouse had a similar pullout program growing up and also reports not getting much out of it, other than a target on their back, socially. Not having a core group supportive of learning gave my kid a lot of trouble in grade 7; although 7-8 is generally a hard time for kids; we're having a lot better experience in 8 at a small private school where the kids all want to learn.
OTOH, I have a cousin who absolutely hated her experience in a tracked system, so I get that too.
There's a bunch of different things all clamoring for more resources in education, and prioritizing is hard, but I think a lot of the conversation in the past few years has been about "why do they get this nice thing? they shouldn't have it" as opposed to "why can't we all have this nice thing" or "how do we make sure selection criteria is not discriminatory".
But I'm pragmatic. Gifted kids can often work more self-directed, so let their class sizes float upwards, and have the other classes float downward.