This is an open question to RStudio (RS). I teach a university course with approx. 100 students and currently use RStudio Cloud (RC) with an Instructor Plan (fixed price + extra cost for over usage).
Due to the amount of students it becomes costly in the months I teach the course and the students are forced to work on the desktop version instead. However, in the months I don't teach the usage of project hours is far below the limit. I guess that RS would like to support the academic community as much as possible. Hence I would suggest that you can buy yearly subscriptions with a yearly amount of project hours. That would avoid extra cost in high usage months and make it possible to continue teaching using RC. Moreover, a yearly receipt would at many universities be much easier to manage accountant-wise.