What happens if the kid can't get a job in the field his angel investors sent him to college for? Would the angel investor just right it off as a bad investment or would the kid still owe a portion of his mcdonalds paycheck to the investor?
This is technically a form of slavery but i guess no more than we already are today where uncle sam expects a portion of your income at the end of the year.
You're right about it being slavery, but the key thing at the end of the day is that the investor sells his shares (even at a loss), and if this poor African kid starts working hard and saving up his money he can eventually start to buy ownership take in himself, until eventually you could own all of your labours by saving and hard work, its similar to the Roman gladiatorial system but without the risk of death, and actually making it meritocratic and humane, which is something that I believe is more important.
The angel investor couldn't just sit around and hope he gets a job, since he spent all this money it's in the angel investors best interests to not only get this kid in the right school, but to also line up employment for him afterwords using his own track record as a referral for a particular position.
This type of system is the only way that I see for large investors to actually be any sort of benefit to the common man, as they would now have an actual reason to invest in people.
Also this is actually being done (to some degree) with sports car drivers and professional atheletes during their training stages, I've actually seen a dragon's den episode where a ~16 year old race car driver wanted to sell shares in his future earnings for promotion and training.