@speechie - My graduate program for speech language pathology asked us to do the same (obtain liability insurance). Luckily you can find an insurance company that has a student rate and if I remember correctly it should only be around thirty dollars a year.
And in my mind, the thirty dollars was worth it for the peace it gave me as far as entertaining thoughts of the worst-case scenario.
Although your school can mandate that you get professional liability insurance, you will likely have a choice as you become a fully licensed speech language pathologist.
For example, I work in the school system and have not been required to get liability insurance. But I would suggest having it whether you are required or not; it is difficult to imagine because it is not talked about much in popular culture but even speech therapists have been sued and taken to court.
You can also ask your future employers if they provide professional liability insurance as part of their employee compensation program.