There was some ruling back in the 1960s (or something like that) that barred the NFL from having games on the same days as College or High School games. I think it had to do with their anti-trust exemption. Dos anyone have more details?
If you look at Wikipedia under the Sports Broadcasting Act of 1961 (http://en.wikipedia.org/wiki/Sports_Broadcasting_Act_of_1961) which references Title 15, Chapter 32 of the United States Code (http://www.law.cornell.edu/uscode/text/15/chapter-32) which defines "Telecasting of Professional Sports Contests" in dealing broadcating TV. Then to quote wikipedia