I am not into the repeating thing. The best advise so far is the one about reviewing his educational history.
Have you 2 agreed on what he expects to achieve by repeating,how does he intend to improve his grades and can he achieve the goal.
Education is good but lets be honest,its not for everyone,infact its not for the majority of people in kenya or the world for that matter. Knowledge is more important and does not necessarily have to come via the classroom.
If he is serious,then i would suggest you sit him down and review a whole range of options including starting early on blue collar career options including farming micro-enterprises etc. which we all know pay equally as well as the white collar paper shuffling jobs we all chase.
And a final word of caution,help him but don't let him become your burden,he may drag you down with him if thats the direction he has set himself on.
I guess if you can't win with facts,you can always pen bile-laced,xenophobic rants to distract everyone.
"The purpose of bureaucracy is to compensate for incompetence and lack of discipline." James Collins