I've looked into this for the last year.

The only objective measure I can find for a school for GT kids is skipping, either grade level or subject wise, and student body ranking as a percentile on national tests, which reflects both the higher intelligence and school preparation.

Here is the list of schools and their NMSF students for this year.

http://dallas-area-schools.blogspot.com/2011/09/2012-national-merit-semifinalists.html

The list pretty much speaks for itself and mirrors what I see when I go to these schools. The majority of the science and liberal arts talent winners come from the schools on the top of the list.

Some highly recommended magnet schools in the DFW area way under perform relative to their reputation.

My first rule of thumb is if there are no kids taking Calculus as 9th or 10th graders, then its doubtful that the school district or private is a good fit for accelerated learners. Its the first question I ask any of the current Seniors.

The top DFW privates all have great reputations and do subject acceleration. Many parents will struggle with public and then move the kids over to private.

The real problem in the DFW area is what to with kids who are 3 to 11 years of age.