It sounds reasonable enough to me given that other NPS sites charge an entrance fee. I would suggest, however, that student groups ought to be able to access the museum, movie, and cyclorama for free. Accoring to Park Superintendent, John Latschar:
We’ve tried just about everything. We’re just not meeting the goals and hitting our numbers.
Nothing was working, so we came to a conclusion that the best thing we
could do is change the fee structure.
Given the comments following the linked article it is clear that for a small group nothing the NPS at Gettysburg does will be viewed as satisfactory. Oh well.