I know if I had ever been the recipient of a substantial sum of money at a young age, even outright, my parents woudl have done everything they could to help me NOT blow it all. And if I chose to, I can tell you, things would have been quite frosty between us had I chosen to ignore all their advice. I can also say I woudl have been really tempted to spend it unwisely.
Also, back in HS, i had some AT&T stock I had gotten as a baby, and dividends were reinvested. When AT&T had to divest back in the early 80's i got about $400. Which to me was a HUGE sum of money. My parents, howver, made me put it in th bank, and use it to pay for books in college. I was not happy with them, but I followed their instructions, and was glad once I saw how much books cost!