Unfortunately, I don't have an answer to the online school, but wanted to give another suggestion to see if it may help. Some background: I've been homeschooling for over 11 years. My oldest is just finishing her first year of homeschool high school & I have 3 kids with sp needs (learning disorders & ADHD --two whom I hs).
Anyway, I can't emphasize enough how wonderful it is to be able to homeschool a child with SN. Your nephew will get customized, one-to-one ratio instruction. A good place to get started, would be to go to your home state's government page & click on education, then click on homeschooling. That way you can become versed in the laws & the high school graduation requirements, including testing (if that's a requirement). It sounds overwhelming, but it's really not. It will actually give you the confidence of knowing how to approach his studies. Also, if he has an IFSP through the school system already, you'll get free resources (tutors in subjects, like foreign language, etc). I hope this helps!
Anyway, I can't emphasize enough how wonderful it is to be able to homeschool a child with SN. Your nephew will get customized, one-to-one ratio instruction. A good place to get started, would be to go to your home state's government page & click on education, then click on homeschooling. That way you can become versed in the laws & the high school graduation requirements, including testing (if that's a requirement). It sounds overwhelming, but it's really not. It will actually give you the confidence of knowing how to approach his studies. Also, if he has an IFSP through the school system already, you'll get free resources (tutors in subjects, like foreign language, etc). I hope this helps!