It's easy to find statistics on differences in average income by education, but harder to find information on the whole distribution. Here is a table, which I made from Bureau of Labor Statistics data on "usual weekly earnings of full-time wage and salary workers."
10th 25th 50th 75th 90th
Not HS Grad 301 374 488 657 887
HS Grad 367 482 668 960 1355
Some College 398 532 761 1111 1560
Bachelor's 529 744 1101 1647 2368
Advanced Degree 588 953 1386 2009 2974
Education raises the "ceiling" more than the "floor"--the 10th percentile for people with an advanced degree is less than twice the 10th percentile of people who aren't high school graduates, while the 90th percentile is about 3.3 times as high. You can get a sense of the overlap by comparing percentiles--for example, someone who's at the 90th percentile for those who aren't high school graduates would be well below the median for people with a bachelor's degree.
For a more detailed comparison, I assumed that earnings followed a log-normal distribution (which is usually approximately true except in the highest levels) and estimated the mean and standard deviation from the data above. The resulting distributions are shown in this figure (I scaled it up to earnings per year):
The figure makes it clear that people without a high school degree have little chance of being rich, or even affluent. People with just a high school degree, however, have a reasonable chance to make it to the upper middle class.