Salary being paid less than offer letter

Dear sir, I am very hopefully narrating my case for a legal favourable solution. My spouce applied for a teacher job in an educational institute. Appointment letter was given mentioning that she has been appointed on a non granted school division. We were convinced that the school.division is eligible for govt grant and within a few months it will become granted. And u will get salary as per govt pay scale. For which they ask for donation. Initially we have paid Rs. 3 lac. Now almost 1 year has passed and not the govt grant has recived nor the school is paying a rs renumeration. On enquiry the authorities are giving irrelevant, non responsible answers. Even if they had paid some montly salary, we would have waited with hope,but they are paying nothing. In offer letter they have mentioed that u will be paid as per govt pay scale and the same has also mentioned in it. She is regulary signing on roll. My question is can I sue the institute for not paying as per offer letter?. Are there chances that the verdict will be favourable for us and we can get back some amout by way of salary. What evidences will be necessary in the court. So that I can collect it. Please advice. Waiting reply eagarly. Regards Amit