At UO, as at most research universities, many undergrad courses are taught by graduate students who are in the process of getting PhDs. The grad student teaching frees up faculty to teach graduate level classes and supervise the research of the PhD students.
Are the undergrads getting a good education? Are the grad students hurting their own education by working too much on teaching? Eric Bettinger et al. find that actually this system is good for everyone. Paper here, InsideHigherEd review here.
We examine graduate student teaching as an input to two production processes: the education of undergraduates and the development of graduate students themselves. Using fluctuations in full-time faculty availability as an instrument, we find undergraduates are more likely to major in a subject if their first course in the subject was taught by a graduate student, a result opposite of estimates that ignore selection. Additionally, graduate students who teach more frequently graduate earlier and are more likely to subsequently be employed by a college or university.