I've seen online programs which range from poor quality to top-notch and excellent. I'm encouraged by the description of this Global Freshman Academy (edX and ASU partnership) program as they do not have a student pay up-front, but only after successful completion and if credit is desired. It seems a great opportunity to try-before-you-buy.
I'd probably have my student inquire in advance (with parental coaching and assistance for his self-advocacy as needed) about the syllabus, grading policies, professor or teaching assistant office hours, and whether there is a cap on enrollment per class. These may help assess the amount of time per week your student may expect to devote to course material, and the level and frequency of feedback your student might receive.
The mix of other students in an online course discussion forum can bring valuable diversity in thought and lived experience and be a tremendous asset to one's learning.
