Dear Kiran, please take one among  Voter Id, Aadhar Card or PAN Card. It is quite unclear what you mean by old school. But the ID proof should be relevant and can be easily identified with you. There should not be any discrepancy. Current school ID can be accepted but an old school ID card might put you on a tight spot. 

No, for Id cards official identity proofs should be produced and this does not include school identity card. Official identity proofs iclude aadhar card, pancard, passport, license etc. Additionally, the identity proof that can be submitted would be said in the instructions present in your admit card along with the rules and regulations to be followed for the exam.