Our school district requires a 96th percentile or above on the OLSAT in third grade. They rank the kids by scores; my son got a 99 on all 3 parts (total, language, math). However, only kids with a 97-98% or above could actually get in, since they don't have enough spots.
This year, they now do a lottery to get in, so if you have 96% or above, you go into the lottery.
It runs one grade level ahead in math and, for my son, two grade levels ahead in vocab, more writing. At least it is something.