You are assuming that the student will be interested in that help, but you can't force help onto someone. How do you prevent the student just taking the money and doing whatever?
How many students will you have to mentor to get a guaranteed return?
Also, teachers typically don't have that kind of investment money, so would have to get funded themselves for that purpose. How would risk management work along that double-tiered, decades-long funding structure? It seems like a good way to burn a lot of money.