I believe that Grand Prairie Advantage is a charter school and may operate several other charter schools in the DFW area.
Charter schools are eligible for UIL membership, but since they are tax-supported schools are not eligible for TAPPS membership (there are three tax-supported schools in TAPPS, but they are grandfathered under old rules -- Texas School for the Deaf in Austin, Giddings State School and Gatesville State School, the latter two are youth prisons. All three play 11-man footall).
It will be interesting to see how many charter schools end up in UIL districts, especially in football, with tomorrow's realignment.