S.C.
http://www.tea.state.tx.us
click on AEIS Reports and then choose your school or district.
Here's the link on the tea website for 05-06. I would be curious to see how they performed this past year. The results to 06-07 should be made public any day now. If the scores improved this past year, then I would not worry too much. There are a lot of reasons why a school might get a low score, including testing scores. It may have to do with how a particular portion of the school's population performed (white, black, etc.) From glancing at the report above, it looks like the testing scores were pretty low in some cases.
After a rating like that, I bet that a lot of personell was moved around (principal replaced, etc.) That campus also probably got some extra support staff to help improve reading scores, etc.
You could call the TEA or Garland ISD and ask them to explain clearly why that school got the rating and what they have implemented to perform better in the future. Also, ask about the most recent scores to see if there was improvement last year.
Good luck, and way to go for watching out for your child!