Side question: Who was the best NBA prospect you've ever seen coming out of high school?
Doesn't matter if they ended up going to college or not, and their collegiate and pro careers are irrelevant; the question is about the best high school prospect you've seen.
For me, It's LeBron. Anyone feel differently?
Problem is, until just a few years ago you just never got to see the best high school players. You tube, nationally televised high school all-star games, and the allowing of 18 and 19 year olds to be drafted by the NBA changed all that. So its really hard to pick anyone but Lebron given what was available to see.
Magic Johnson might be the best ever though given what he did right out of high school his first two years(NCAA Championship and NBA Championship).
Depends on your region, I'd think. As someone from New England, I remember hearing about Michael Beasley while he was playing high school ball. Camby and Ewing were before my time, but I've heard second hand evidence of their high school awesomeness too.
I would imagine there'd be a bunch of New Yorkers who would have interesting stories to tell on this front, although they're probably not lurking CB. 
I actually saw Ewing play at Cambridge R & L in 1981. He was amazing but he was also playing mostly against 6'4" centers. He didn't have the skills that the 18 and 19 year olds that are top recruits nowadays do. He was extremely raw.
If a 18 year old Nerlens Noel could have played an 18 year old Patrick Ewing, Nerlens probably would have won that match up and Nerlens was considered pretty offensively raw coming out of high school as well.
Ewing had the much better physical tools to build his game around that Nerlens doesn't have. But at the same age, Noel might have been a better all around player simply because he was playing the game younger and played national level talent in AAU ball in high school.
Ewing would have probably lost a match up against an 18 year old Dwight Howard or Anthony Davis as well.