I went to a very small school, so I took grade 11 and 12 physics by distance learning (in fact I was the only one taking grade 12 physics at my school in that particular semester). It's VERY easy to procrastinate on courses like that, so if at all possible make sure that he has some deadlines. For both of those courses, I was supposed to spend the entire second semester on them... I ended up starting in May and squishing the entire course into a month and a half to meet the final exam deadline. I did quite well, but it's definitely not recommended. :P I personally learn really well by reading things on my own, but that's a personal learning style of mine, and a lot of people learn best in different ways than that. It'll be harder than in a classroom, but it's nowhere near impossible. The hardest part is getting a source of motivation.
Also, if he has any friends that would be interested in taking physics with him, that would probably help a lot. If you work together with someone and say "let's get assignment _____ done by ______", you're a lot more likely to actually do it than if you're on your own.