[Resolved]  Delhi Public School Navi Mumbai — not returning the original birth certificate of my daughter

My daughters studied in Delhi Public school for 5 years,at the time of admission thei Original birth certificate was asked to submit in the school,which I did, But the school authorities are not returning it back even after the children are not studying in that school from last 2 years. I am badly in need of their certificate for their admission now? So my question is ,is it a rule of CBSE schools that not to return the Birth certificate of the child once they are admitted in a school after receiving it at the time of admission.?