Head teacher denied to return TC

Hello sir /mam.. I am student of class 12th and currently studying in CBSE Patrachar vidyalya situated at Ramesh Nagar new Delhi as I was failed in class 11.. It is one of the branch of Patrachar whose head office is situated at Shalimar bagh .. At the time of admission they asked for yearly fees (24000 for regular classes) to submit but I told them my financial problems so they agreed for installments (2000/month) later I realised that study there is not much good so I decided to go for home study option which costs 10000 . I was also unable to pay that sum together so I asked them for return my Tc back to me because I've heard that same form of home study will costs only 500 at Patrachar head office Shalimar bagh. So I decided to go there but they refused to give my Tc and told me that I have to give them 13000 in order to get Tc . And now neither they return the Tc nor they are allowing me to sit in the class...in both cases they are demanding 13000...what should I do? As I'm an orphan ,living with my sister and her husband we are not financially able to fulfil their demands....