I went through the GISD school system myself, but that was quite awhile ago. I was sad to hear recently from an old high school teacher how bad South Garland HS has gotten over the years.
When we moved back to Garland I wasn't looking forward to choosing a school for my daughter to attend in the district (GISD has choice of school, so as long as there is room in a given school you can enroll your child, regardless of your proximity to the school). I visited a few & looked at the stats and went with Armstrong, which is located in Sachse. My daughter loves her school & I don't have any major complaints. I like the small-town feel of it, if that makes sense. My daughter is in first grade & has 17 other children in her class. She loves it.
Good luck!