More Missouri high school students got good grades on Advanced Placement tests last year. The exams are graded on a scale of 1 to 5, and colleges give course credit to students who receive scores of 3, 4 or 5. The Missouri Department of Higher Education reported that more than 4,600 seniors who graduated in 2010 had scored a 3 or higher on at least one AP exam during their high school careers. That’s about 300 more than in 2009.