I was doing that, teaching full time as a visiting lecturer, TAing full time then required to ALSO sit in the Chinese grad students TA classes to handle the Questions they couldn't handle in English. The lecturer position made enough money to pay the fees that weren't covered by my TA work. The covering for the Chinese grad students, that was done because the profs required it, no pay.
While being a full time grad student.
When I told the grad director that I didn't have time to cover for the Chinese grad students (whose English skills were almost non-existent) he told me that if I didn't cover for them, my grades would suffer.
That is 'grad slave' work. Being told that the unpaid work you're doing to cover for others who couldn't do their job, will affect your grades.
But feel free to just assume I'm lazy because anyone who works full time and also wants to pay to attend college full time must be lazy.