By my rough count: Jackson, Van Buren, Fillmore, Lincoln, Johnson, Grant, Garfield, Harrison, McKinley, Harding, Coolidge, Hoover, Truman, Eisenhower, Johnson, Nixon, Reagan, Clinton, and now Obama (who had things much easier materially than many of his predecessors.)
This doesn't seem to indicate that only people from wealthy backgrounds can get ahead in America.
OK Bush’s dad was the head of the CIA, when he ran a small oil business in Texas, with about 23 employees, and lived in a modest low end middle calss house, no comparision to the one the O lives in.
He did get a Harvard MBA, which is a light year better than a JD.