How played pro baseball without going to college?

Answer 1

You can be drafted by a Major League team straight out of high school-- many people are. After graduating high school, you have to make the choice about whether or not you want to sign or go to college. If you go to college, you can't be drafted again for three years, but if you go to a community or junior college, you can be drafted at any time.

Bryce Harper did something highly unusual. After his sophomore year, he earned his GED (a requirement for high school players who want to get drafted), and then dropped out after his junior year. Then, he went to a junior college to play Baseball for one year, and made it to the Junior College World Series at the ripe old age of 18. Then he got drafted, and made it to the big leagues before his 20th birthday.

This is not common.