FO- You're correct, only 20 total, but not just from high school. There has been 20 players gone straight to the majors after being drafted. Only four of those 20 were from high school.
After some research, here are the names:
1. 1967- Mike Adamson, South Carolina
2. 1969- Steve Dunning, Stanford
3. 1971- Burt Hooton, Texas
4. 1971- Rob Ellis, Michigan State
5. 1971- Pete Broberg, Dartmouth
6. 1972- Dave Roberts, Oregon
7. 1973- Dick Ruthven, Fresno State
8. 1973- Eddie Bane, Arizona State
9. 1973- Dave Winfield, Minnesota
10. 1973- David Clyde, Westchester HS (TX)
11. 1978- Mike Morgan, Valley HS (NV)
12. 1978- Brian Milner, Southwest HS (TX)
13. 1978- Bob Horner, Arizona State
14. 1978- Tom Conroy, Gateway HS (PA)
15. 1985- Pete Incaviglia, Oklahoma State
16. 1988- Jim Abbott, Michigan
17. 1989- John Olerud, Washington State
18. 1993- Darren Dreifort, Wichita State
19. 1995- Ariel Prieto, Fajrado University (Cuba)
20. 2000- Xavier Nady, Cal-State Berkeley