Which school has the highest strength of schedule rating of all time? The Indiana Hoosiers.
In fact, the top ten SOS of all time belong to the ten original B1G schools. Indiana, Wisconsin, Michigan, Illinois, MSU, Purdue, Minnesota, Northwestern, Iowa, and Ohio State, in that order.
Mizzou is #25 all time in SOS.
http://www.sports-reference.com/cbb/schools/