Rachel Gross emerges from a classroom to face the crush of students charging through the corridors. The labyrinthine hallways and riot-proof walls make the UW Humanities Building feel like a medieval fortress under siege during class change. Gross has just a few minutes to herself before her next skirmish -- with a room of 13 undergraduates.

She is a fifth-year graduate student studying environmental history. Her focus is the history of outdoor clothing and gear. She's finished her master's thesis -- "Synthetic Wilderness: Gore-Tex and the Paths to Mastery in Outdoor Recreation" -- and is now working on her dissertation. In order to earn tuition remission and fund her research, Gross is also working as a teaching assistant, or TA, this semester.

Teaching assistants are graduate students who work for the university in exchange for tuition remission, health insurance and a living stipend. They are paid little and work hard for their keep. A typical TA with a 41% appointment might make $12,091 in a year. And there is no question the University of Wisconsin-Madison could not operate without them. TAs teach half of all lectures, discussions and labs. In the College of Letters & Science, home to almost 70% of the university's TAs, graduate and professional students teach more than 85,000 credit hours.

"Grad students do wonderful work on this campus, and I don't know how we'd get along without them," says Brian Bubenzer, assistant dean for Graduate Student Administration.

Bubenzer allows that being a TA "really is a balancing act." They must cope with the pressure of their own studies and tend to their personal lives.

"We've all heard horror stories," Bubenzer says, referring to graduate students who end up living in the library or their office. "Grad student lives are very complicated, and we do ask a lot of them."