I'm not sure exactly how your system works, but I would assume it's fairly similar to here. I'm also assuming revisions are exams?
I'm almost 2 yrs out of university now and am still studying lol. That's what I get for choosing to be a military pilot I know that what motivated and still motivates me is having a goal that I have set for myself. I was lucky and knew what I wanted to do by grade 10 (15 years old). This was in part thanks to my parents talking about different jobs at the dinner table. They never really nagged on me about my marks, but my Dad did explain to me that the best way to keep my options open and likely get my dream job was to do the best I could at everything. He mentioned that it's the people with the best marks that often get to choose exactly where they want to go. It definitely keeps lots of doors open! My Mom also brought up her experience since she had never finished University (because she had me) and never went back so now didn't really have many options for jobs she could do.
Knowing what I wanted to do so early on really helped my focus and drive to get good grades. If I could go back though I would try harder in high school. Because I was naturally good at school and didn't have to try too hard for good grades, I didn't study much. That made for a really hard first year at university. I did my first year in engineering and almost failed! I had a D average and actually failed a couple courses. I was heart broken and couldn't believe I had done so poorly, but it was because I expected to be able to coast through like high school. The best thing my parents did for me was to let me fall that hard. Sure they tried to keep engaged in how I was doing and offered help if I needed it, but overall they let me learn through experience. When I came to them frustrated with how I was doing, they listened and said "well, it sounds like you've got two options. Keep trying to coast through and take the marks thrown your way OR start really studying and work hard for the mark you want." I changed programs and started to work harder. In the end my marks came way up (graduated uni with a B+ ave including that first year).
Base line here, I had to have a goal and had to experience it for myself. My parents being there for me and offering help if I wanted it was great too. I'm so glad they didn't push me though and instead just guided me and then waited for me to come to them. It's a hard thing to do, I'm sure and I have all the more respect for them because of that! My advice to you? Show him different options and what he needs to do to get there, help him set goals for himself, and then be there for support if/when he needs it.