Actually, I don't think differentiation is best as a policy. It's the only form of adjustment for GT kids that can actually result in a GT kid being effectively HELD BACK: if the child has a teacher who is great at differentiation one year and one who does no differentiation at all the next year, it's just like being held back--possibly more than one grade, even!
Honestly, I can't think of a much worse situation for an HG+ child than to be held back and have to repeat material after being allowed to jump ahead.
I would always prefer anything that is codified and given the official seal of approval of the bureaucracy; those adaptations are much harder for anyone in the school to undo.
That's not to say that differentiation doesn't help a kid, and done well, it can absolutely be a lifesaver. But it would NOT be the policy I'd be asking to get implemented. I think it's a pretty high risk option that relies much too heavily on the support of individual teachers, with no real bureaucratic force behind it to see to it that it happens daily and it works and it keeps on working for that particular child through all of the years of school.
Just my $.02...
