It shouldn't be illegal, because the teacher didn't take the money, but it is unreasonable for him to do so, and parents have the right to refuse. Moreover, it is against the educational concept for him to do so, so he can sue him at the Education Bureau. Because some children have slow brain development. Not as fast as other children, can you always pay the bill? And use money to coax children to improve their learning enthusiasm. This is against the regulations of the Education Bureau.