In this context, Gaussian is a pretty useless assumption without fixing a variance. Proposed alternatives range from "already implemented" to "totally infeasible" depending on variance.

> which tests seem to verify

Not really. For each individual subject area, maybe, and again, Gaussian is pretty uninformative.

But the odds of a student being "average" in every subject area != the odds of a student being "average" in a given subject area.

> whose level there are ways to accommodate anyway in most school systems

Except the whole point is that there are not currently ways to accommodate this in most school systems! From GP:

>> Schools (at least around here) do not hold kids back anymore. No matter what.

Also notice that holding back a student in math is possibly net detrimental if the student is not also behind in English and Science.

> but also about sharing the same teenager and adult-making experiences as other kids of your age, which is probably even more important that what's actually taught

Again, the prepubescent/tween/teen division is much less granular/restrictive than the competency-by-age-X division.