Help

I'm Working in a company. It has been almost 6 months. And I am also studying at college. But now i cant handle both at same time. So now i want to leave my job but my employer told me to do notice period of 3 months otherwise i have to pay that 3 months salary to the company. But I'm not able to serve notice period. Notice period is compulsory? Can I take leaves when I'm on notice period? Additionally They took my original 10th Certificate. And I have also Signed on Confirmation letter. Here is the condition of notice period which is mentioned in the my signed confirmation letter - Notice Serving Period In case of any situation of leaving the title, a written application (Resignation) must be submitted to the company. You will need to serve 3 Months of your Service after your resignation is approved. Meanwhile you need to prepare/train a staff member who can work on your behalf with the same professionalism that you had. Please guide me what should I do?