There is a fee charged to enter Yellowstone Park. However, National Park Service (NPS) regulations allow school groups, national and international academic institutions to obtain an Academic Fee Waiver (AFW) for entrance fees, provided the visit is for educational credit or scientific purposes, and the resources or facilities the group proposes to use support those purposes. An AFW is not granted automatically. Applicant groups must show they qualify for the AFW by meeting 3 criteria: eligibility, educational purpose and relevance of park resources or facilities.
YSC doesn’t provide this AFW application service. Schools need to apply for the AFW at least 3-4 weeks before they plan to enter the Park.
The NPS link for the AFW Program: http://www.nps.gov/yell/planyourvisit/acfeewaivers.htm