We are in a school similar to your previous one (Gov award, 9 rating, etc.) and there was little differentiation in kindergarten although the standard was a little higher overall. I'm with you in thinking the "advanced" math curriculum should just be the standard curriculum and isn't very advanced at all. It will be even more confusing this year though since there is a new math book by Pearson called enVision Math being used and it is even more basic than what the standard FCPS curriculum describes for the younger grades at least. Until FCPS and school principals make it a priority to make sure their advanced math program is implemented well, it will be implemented differently teacher by teacher and school by school and in some schools may not be implemented very little. A friend of mine did talk to a teacher before starting at Vienna Elementary and said it helped and they are happy there. Maybe try this? There is also a Vienna Moms Vienna Elementary subgroup you could join to ask more questions although at least half of the parents there have preschool age children.
http://www.viennamoms.org/