[kwhitefoot]

> takes children years of full immersion

Perhaps it depends on the language you start with and the one you learn but small children seem to pick things up very rapidly by immersion.

It took each of my children roughly six months to learn Norwegian from the age of three when they went to kindergarten. We kept them at home until then to make sure that they would be fluent in English, then sent them to kindergarten where they learned Norwegian without any formal lessons at all, and within a year they were indistinguishable from the natives.