Most of my information comes from books that I either own or borrow, but I do have some links showcasing that Republican support in regards to education is similar to a bell curve and Demcratic support is similar to an inverted bell.
This information is from the Pew Research Center and it indicates Republican support is strongest with college graduates and those with some college education .
CNN has a nice setup featuring the exit polls from the 96-04 US presidential elections. Even in 1996 when Bill Clinton soundly defeated Bob Dole, the Republicans still won the college graduate demographic. Also, the Democrats largest bloc in regards to education is almost always those with less than a high school diploma. When I take this into account, it would seem to dispute your assumption that Republicans have a "vested interest in keeping peoples academic achievement at a bare minimum."
http://www.cnn.com/ELECTION/2004/pages/results/states/US/P/00/epolls.0.html (
http://www.cnn.com/ELECTION/2000/results/index.epolls.html (
http://www.cnn.com/ALLPOLITICS/1996/elections/natl.exit.poll/index1.html
