Dear Mazharuddin, your 12th final marks sheet itself is proof of you completing your 12th class. In Bachelors degree and above, you get a Provisional Certificate along with our Degree certificate. But for 10th and 12th classes, marks list is the proof of a candidate either passing or failing that particular class. When you are leaving your school after 12th, you will get a Transfer Certificate. This is the proof that you have studied in that particular Institute.