Hello Student

In your query you have not mentioned the name of the school and the authority of the school so it is a little bit of difficulty to prediction something  perfectly. If it is Navodaya vidyalaya then you have to apply for your admission number on the other hand it is called registration number, in the official website of Navodaya vidyalaya samiti which is under the Ministry of Education and it's that means Navodaya vidyalaya samiti chairman is the Honorable Minister of Education, government of India. So for your required enquiry and to get solution for your problem to reset your admission number again from the authority you have to apply on the official website of Navodaya vidyalaya samiti Delhi.

Hope this  will help.