Work on a Student Visa?

Hi, I need your help:
a Chinese Traineeship agency proposed to me to work full time (5 days a week, 40 hours a week) for 6 months and getting paid 1500 RMB for a hotel chain in Beijing on a Student (X2) type, while attendong school only one day a week. Is it legal to do it? The Chinese Traineeship agency told me it is, but I have doubts about it. In case I’d accept it and while in China I break the contract, what repercussions I would have? Thank you!