I do not get the impression (at all) that grades are that narrowly bunched together at DC’s school. The profiles others have posted to this thread similarly suggest that the student bodies at other BS’s have a range of GPAs. That said, I would not be surprised to see some grade clustering in view of students having some latitude to select classes at a level that will challenge but not break them.
Although I don’t think boarding schools should water down their grading, I have to confess that I’m somewhat troubled by the level of grade inflation that exists throughout the country. See, e.g., http://talk.qa.collegeconfidential.com/high-school-life/2005522-as-on-the-rise-in-u-s-report-cards-but-sats-flounder-p1.html. To my mind, there’s something wrong with 47% of the nation’s high school graduates having an A- or better GPA. To me, that really diminishes the value of GPA.