Are freshmen courses taught mostly by temporary or part-time instructors and by graduate assistants?
This varies by department. In some departments almost all freshman courses are taught by full-time faculty. However, in some departments, a significant portion of freshman courses are taught by graduate assistants, adjunct faculty or a combination of faculty (lecture sections) and graduate assistants (lab). Typically, such courses are introductory courses with numerous sections. Still, some sections of these courses will be taught by full-time faculty, and your student may choose one of these sections. It is important to note that having a graduate assistant or an adjunct faculty member is not a bad thing. Graduate students are top students pursuing advanced degrees in their fields of interest. And adjunct faculty are typically people who have excelled in their field of expertise outside of the University environment (for example, a newspaper editor who agrees to teach a Journalism class).
