Homeschooling takes a lot of time, energy and planning.
This is what he will need to be admitted to a decent college (requirements vary, but these are the basics)
4 years English (grammer, comp, lit combined into one course for the year)
(American Lit , British Lit, and World Lit and one "other", you could just call it 9th Grade English)
Also one course (1/2 credit in Advanced Composition)
3 years Social Studies: American Government and Economics are usally 1/2 credit courses, then one year of American History, one year of World History.
3 years of Science Biology, Chemistry and Physics (TWO WITH LABS)
2 years of a Foreign Language (same language)
and additional electives to make up 22 - 24 year long classes or credits.
Classes might include Introduction to Computer Literacy, Health (1/2 credit), Sociology, Introduction to Historical Biblical Analysis, Introduction to Research and Research Paper, Georgraphy, Pre Calculus, Trig., Philophosophy, etc...
Many colleges require that homeschoolers take SAT II tests in addition to the SAT in order to be considered for admission. Some only require 3 tests , some require as many as 7. This is so they can validate that your student really learned what they claimed to learn on your transcript (that you need to provide....there are transcript software programs out there to buy). Many colleges require homeschooler's SATs to be as high or higher than the "average incoming freshman's" SAT.
There are correspondance high schools that might be accredited and may, upon completetion, issue a diploma just like a regular high school.
Hope this helps.