Julie,
I agree completely. Not only isn't it NOT a "dumb" question, if you are a senior in high school and just now coming to grips with the grades issue and their full impact, they are tremendously important questions being asked by Southern Belle.
For whatever it is worth, the idea of going over the head of the principal isn't one I would endorse based on what I am reading. If it is true that one other student is being allowed to retake a class, one might assume the principal has a reason for the decision. Maybe the principal actually thinks this is being too heavily influenced by baseball and wants the student to "learn" his way out of past mistakes before he makes more in the future. Maybe that is giving the principal too much or too little credit but I would be thinking through those possibilities before I went over the principal's head.
We have no way of knowing, but from reviewing one past post, the student has not been doing well in school for awhile. At some point, whether it is now or in college, doing poorly will certainly catch up unless the student changes and/or it is recognized the learning disability is strongly associated with the academic issues, or both.