I don't live in texas and my son is only 2 so I don't know the school-system as a parent, however my husband is a (middle school) teacher here (in NJ) and I've taught ivy league freshers, so seen the 'end product' of some of the best and brightest high school education.
My tuppenceworth:
(1) Universities ARE very expensive. $40K per year is not unheard of. HOWEVER Most good ones offer scholarships for all kinds of things, not just sport, and most offer bursary support, means-tested fees, and other kinds of help. Few students at Harvard, for example, are paying full whack because they have the funding behind them to ensure that if you pass the exams to get into Harvard, they will find the money for you to go. Harvard's very rich. Not all universities are, but most have a long standing legacy of financial aid. So perhaps, depending on your circumstances, you're actually only looking at $20K or $30K a year. still not cheap, but frankly, no is uni in England these days. I've worked at a few universities in the NJ/NYC area, and certainly most small liberal arts colleges have less than 20% of each incoming class year paying full fees. Most students are on varying amounts of scholarships, financial aid, and bursaries. So far, so good! EXCEPT.... non-US-citizens may not qualify for lots of them. So get savvy.
Most students have jobs on campus, and some 'work-study' jobs literally cut the cost of their fees, instead of paying out cash. I suggest when you're looking at universities, look at what kind of financial aid they offer.
(2) Students who have studied A levels or the IB are further ahead when then go to university than students who have done standard SATs and any college entrance exams. The A levels are more rigorous, intellectually demanding, and require more abilities (essay writing, construction of argument from available sources, etc). I taught very very clever freshers at Columbia Uni (Ivy League in NYC) who couldn't do things that you'd need to do in A levels, in England and Wales.
BUT:
Students who do a 4 year BA in America are no less educated and prepared for the workforce than students who do a 3 year BA in England. I think it evens out pretty well in the end. Students tend to live on campus, in uni housing, for the whole of their degrees, however, so have to do things like learn to pay a gas bill or deal with a landlord after graduating, rather than as part of the uni experience.
In my experience American undergraduates are a bit more coddled -the university views itself as 'in loco parentis' and students are spoonfed a lot more. That said the BA is a broad-ranging and challenging thing at most good universities here, and students can decide 2 years into a degree that (For example) they want to be a doctor, rather than having to make up their mind about that at aged 16 as in England.
Law, Medicine, vet etc are post-grad degrees here in the USA. You need to do a BA/BSC first and then apply to law school.
All that taken in to account, I would rather my children did A levels or IBs, and DH (having taught in the UK and the USA now) feels that our state schools are better. (Private schools depends on area - New Jersey is heaving with them). But it's a bit far off for us to decide at the moment!
Hope some of this helps.