The movie starring Kevin Costner is the No. 1 reason so many Americans get better but not great grades.


In fact, 90 percent of students in the United States score lower than their peers on a math test, and one-fifth of those students can't read a word they write down, according to a study released Tuesday.


The average high school student in the U.S. has trouble taking an advanced math course, and is usually written off as "failure" on a