For people not aware of the geography referenced here: Leander and The Woodlands are both affluent areas outside of the major cities referenced.

I would suggest that the students here are doing well due to a combo of the following factors:

Smart parents live here, and they have smart kids

Rich parents spend less time fretting about paying bills and more time helping kids with homework

One (rich) parent works, one stay-at-home parent takes care of the home -> more time with the kids

One parent is involved with the PTA, which correlates well with student success

And to he clear, I'm not casting judgment. I live in Frisco, Tx. We are enjoying ALL of the above benefits

As someone who lives in Leander, I would say Westlake is the affluent area of Austin and Leander is the up and coming suburban middle to upper middle class area. Leander ISD has some great schools and some bad schools and historically wasn't great.

Adding on:

Well educated parents are more likely to have the skills themselves to help with homework and are more likely to put more emphasis on academic performance.