There is no question the courses are rigorous, however, please note that as long as the student shows any effort, the professors will go out of their way to make themselves available to help the student. Unfortunately Dartmouth treats GPA’s from the partner LACs the same regardless of whether the academics are more or less rigorous at the various partner colleges. Did your son apply to any of the other participating colleges with the Dartmouth program? https://engineering.dartmouth.edu/academics/undergraduate/dual/. Some of these are academically less rigorous and easier to get into. I think there are few on this list where the RD application deadline is February 1st, such as Hobart William Smith and St. Lawrence.