There is a student visa available that allows for work. I know that this the case in Chengdu. Many non-native English speakers use this visa to hold down jobs. In my case I was denied a new work visa because I have been here for more than five years. I enrolled at a University for some language classes and applied for this visa. The visa stated that I was allowed to work but I did need to attend classes. In your case it sounds like the agency is taking advantage of this visa with no plans for you to attend classes. They are probably paying a staff person at a University to fake your enrollment. Could be trouble.