Can school demand full year fees to give Transfer Certificate?

Dear Kaanoon community, On May 9th I had applied for a transfer certificate for my elder son who's studying 12th Right now from a cbse school in Chennai. The school had not responded properly citing that the principal is out of station. Finally on 30th may the principal had come back and I spoke to her. She was ready to issue the TC but only on the payment of the fees for the whole year. Which is unfair in my opinion and wrong. Can the school do this legally? Is it illegal? What should I do and how should I respond? I am not ready to pay the whole fees. The school had started in the month of April. At that time they had collected a fee of roughly 10,000 +-500 for issue of notebooks, uniform and other miscellaneous items which is again illegal as far as I remember. My younger son is also studying in this school and I am scared if there is a problem, the school management might trouble him and create problems for him. Is all of this legal what the school is doing? How do I respond to this? Thank you all in advance. With Regards, Gopal Agarwal