What action can be taken against illegal termination?

Hello, I have been working as a teacher at Saint Patrick's Vidya Bhawan, Jodhpur, since November 16, 2021. My contract period was for one year, and the probation period of two years will be completed on November 16, 2024. According to the school's policy, teachers are made permanent after three years, and I have completed my tenure of 3.5 years. I was supposed to be made permanent in April. However, my principal gave me a termination letter, stating that I am considered an "extra teacher" and that they are terminating my employment. On the other hand, a teacher who joined six months after me is being made permanent because she is Christian, and the school is a Christian institution. There are six other temporary teachers after me, and I am the senior-most, who was about to be made permanent. They have never given me any warning or negative remarks. The only reason they gave for terminating me was being an "extra teacher," which seems invalid. What should I do in this situation? Please guide me.