Before DD6 started K, she did outside testing and I asked for subject acceleration in math and reading. She's now in 1st and doing subject acceleration with 2nd grade for math and reading. It's been a good short term solution for us since there is an accelerated magnet program that starts in 3rd grade.

Tamara Fisher has some good blogs on this subject:
http://blogs.edweek.org/teachers/unwrapping_the_gifted/2010/07/abandoning_age-tracking.html
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Ironically, the grade-level, whole-class groupings apparently preferred by these teachers who bemoan ability-grouping are the most restrictive form of tracking, that by age. For a century (-ish), schools have "tracked" students based on when they were born, not based on what they are ready and able to learn. "Born between September 1, 2003, and August 31, 2004? You belong to the Class of 2022." That is how it works in nearly every school in our country. It's tracking by age, but no one calls it that.

http://blogs.edweek.org/teachers/unwrapping_the_gifted/2010/09/what_matters_most.html
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Reaching each learner in his or her zone of proximal development requires that we give higher importance to learning and academic growth than a social egalitarian ideal of everyone reaching the same finish line.