I have been a Texan for 13 years but not from Houston. TX is one of a better state for gifted education. But it largely depends on the school district. Houston has many school districts and not all are created equal. There is a gifted school for elementary school in Spring Branch. Most of the schools have gifted education classes in cluster. Houston ISD has magnet program.

http://www.houstonisd.org/Page/120585

Katy and Fort Bend are good as well.

But if your DC is a PG, it will be hard to find a good fit anywhere.

Good luck!