College Prep Private HS options?

Anyone knowledgeable about US college-prep private high schools? My husband and I adopted three daughters from China when we were already well along in years, and are now itching to relocate with our youngest in tow. DD studies French and Chinese but no Spanish, though I expect she will pick it up if she were immersed in the language (although we are looking for a school that teaches in English). She will be in 9th grade in September. While public schools have definite appeal, she is a workaholic overachiever chomping at the bit for a rigorous college prep education, and it looks like a private school is her best bet.

I will read the schools' websites, possibly make phone calls, and definitely visit sometime in the coming months, but I thought I would ask here for first-hand experiences and ideas. Websites can be deceiving.

Also, if we relocate to CS, we would choose a school in a desirable neighborhood, of course, and choose to rent (and then purchase?) a residence near the school. So a noisy city does not appeal. There are a number of HSs in Guanacaste.....?

Thank you!