Our school system has 2 GT programs in elem-- one is self selected enrichment based on interest. The other is enrichment based on teacher recommendation and replaces language arts. For late elem math and for middle school 4 core courses, there is a test for GT. Few qualify based on test. 5th grade teachers recommend the vast majority of participants and if that doesn't do it, then parents can appeal, and pretty much get their kid in if the child is not disabled (grr-- fortunately, my 2E tested in) or disruptive.
Then for high school, ANYONE can chose GT and the grades are weighted. GT basically has an extra project thrown in on top of the curriculum at middle and high school, so really any motivated kid who can do regular can also succeed in GT. For math, there is zero difference, except that you get to the class earlier in your school career if you are GT. You can be a senior who struggles in math and take algebra 2 GT to get that weighted grade. There is really no reason not to take the GT version of math.
Despite being a program that ANYONE can choose, we have the same problem with demographics. Nobody is excluded in high school, but there's something going on that makes GT not an attractive choice for low SES (though racial diversity is not as much of a problem)
