Having witnessed my own friends, I simply do not believe that people who can juggle exist.

At that point it doesn't really matter, because K is really about play and learning the conventions.

By the end of 2nd grade it was clear that they were bored out of their minds. So to private school they went.

For parents with kids that aren't motivated it's hard to understand what the fuss is.

But, the Left's problem is that instead of trying to raise everyone up they're bringing people down. It was that way in the USSR, and it's that way here. Where I used to live the Talented and Gifted program (which was state mandated) had a $1000 budget systemwide. The "equity" fund was almost a third of the budget. At that point why bother with public schools? It's taxation without representation.

It's not only those who are failing that need help. (And I agree they shouldn't be treated as defects)

But gifted kids do exist, and they have all sorts of existential questions and concerns that other kids don't tend to worry themselves about. Unaddressed, these kids end up miserable, depressed, and anxious... which is why it's important to pay attention to them too.

Whether Kindergarten is the right age is a different question, but to imply that only those failing need help is simply untrue.

Individualized education would be ideal, but close to impossible, for obvious reasons.