At school, we have a computer that is only for students to login to and do computer science related activities, such as compiling C and C++ programs for classes. It was running some obscure flavor of linux that was put on many many years before I took it over. I have recently installed Ubuntu Server on it to make it more maintainable and secure. Currently we set up user accounts as needed. Students ssh login and complete assignments for class and each user stores their work and play in their home folder. The instructors will have the students leave their work in a certain folder for submitting or something like that.
My concern is a user that gets too exploratory and explores or someone maliciously trashes it and breaks something, thereby causing no one else to be able to get any work done, and results in the faculty complaining to me and making me look like a bad sysadmin for not preventing this. (I am still an undergrad and at their mercy)
The students are currently in their own group, and can only see their own home folder / can't browse other students folders. Faculty have more advanced accounts but not admin accounts. I am reluctant to start changing permissions on important system folders worrying that I may break something (again as I have done before).
What safety measures can I take to ensure functionality of the system while keeping it secure so everyone can enjoy and use it?