I'm totally not convinced!

In Vancouver it was decided that kindergarten students with English as a second language would be entitled to full day kindergarten while those with English as a first language would be entitled to only a half day. The idea being that the those with English as 2nd language needed a little more of a head start. Of course this meant that the kindergarten classes were effectively segregated.

What has actually occurred is that because the the 2nd language kids were segregated, their language acquisition has actually decreased because they have no playmates that speak English.

Kids learn more from each other than the learn from adults. If you want them to learn from each other (this also includes tolerance for differences) they have to learn it from each other, not from an adult standing at the head of the class. It is up to the teacher to act as a facilitator for the transmission of knowledge, not to arrange social groupings that have nothing to do with the reality of society.