This line of thinking is why so many families, including my own when I was growing up, find Aledo to be such an attractive option.
My wife and I don't plan on having kids any time soon, so hopefully this whole school issue is somewhere close to 10 years away, but it is something I have in the back of my mind.
Experiencing All Saints and then moving to Aledo, I'd say private schools aren't worth the money. I received an excellent education from Aledo, got into TCU with excellent scholarship money (and every other school in the state of Texas), and felt more than prepared for college when I stepped foot on campus.
For a lot of people, the grandparents may be footing the bill, or money may not be an issue. But unless I hit it big in the next 10 years, my kids will be going to public schools. Especially in elementary school.
I think it depends on what your goals are and who you are as a person.
If you are self driven - then where you go to school and what the environment is like is less of an issue.
If someone is trying for TCU, Baylor, etc that is a different goal then an Ivy, Duke, or Stanford.
If you are expecting a scholarship (athletic or academic_ to support your college education vs someone pay for it - that is different also.
As I said, I have it all in the youngest generation of my family and each kid has different abilities and focus areas - so each wants a fit for them.
But in general, I will be honest and tell you that there is a difference in the quality of education the Big 3 private schools are providing vs public schools even if you go all they way from Tanglewood GT through Paschal Honors/AP.
I am not saying that difference is important to everyone or that every kid will benefit from it or will be hurt if they don't have it.
But there is a difference.