The short answer is no, they won't accept high school courses, no matter how strenuous. The reason is that the State Board of Accountancy requires that coursework be done at an accredited school, and the accredited schools are limited to some colleges and universities - even work at some colleges, you should know, would not be accepted by the Accountancy Board as valid towards the education requirement.
Sam Lee has the right idea; as long as the work is done at an accredited school it counts, so you don't have to spend big bucks for prestige. But no high school work is going to count, sorry.
One final word, though, about the CPA exam. It's as tough as any test gets. The four exams require 14 hours time total, only about 10% of candidates pass all four sections on their first attempt, and that comes after you meet the education and experience requirements. If your son wants to pass the exam, he needs to be really, really ready for it, and while you can spend less at a community college for the non-accounting work to meet the education requirements, I would strongly advise him to attend a school for his accounting classes that has a good record of passing the CPA exam.
I found a web site for Wake Forest, for example, which mentions in passing that USC students are among the most likely to pass the CPA exam. Business school ranks first in CPA exam passing rate | Old Gold & Black
Also, Becker Professional Review (a very well-regarded private CPA preparation course) awarded scholarships for accounting excellence to a students from schools which included Cal Poly, Cal State Fullerton, UCLA, and Cal State Northridge. http://www.beckercpa.com/about/news/...2009_FINAL.pdf
And I know it's a bit down the road, but the right internship with a good firm can provide mentoring and tutoring for final preparation.