Grades running around students' averages!?!?

This morning I went through and looked at all of my band students' grades, to compare them to the grade they have been receiving in my class on the new standards based grading platform. I was somewhat surprised to see that the grades they have in my class right now are right about the average they have in all of their other classes. Students that have a 4.0 currently have an A, and students averaging around a C in other classes are at a C or B in band... In the past I would have seen a lot more As in band. This observation supports this grading platform, and the results are indicative of each student's average aptitude in other classes. When the semester is over, I will compare average GPA to band/choir class grades, and do a comparison between first semester (traditional grading) and second semester (standards based). I am guessing the standards based grading will be more along average, and not make band/choir a "GPA booster." We music teachers will sometimes advertise our classes as being GPA boosters, but are we really educating students if we aren't holding them accountable to the educational material?