Dear Fawad,

   As per CBSC rules you can reappear for your class 12 boards as a private candidate in the year 2019.

Wishing you all the best !

Dear student,

I would like to suggest you that there are very less chances that your school will re admit you as a student as you have failed. So what you can do is either try for some other school or you can go for Private. The procedure for giving exam is to find out a school which allows you to do so. Fill up the documents there and prepare for your exams. 

All the best .I hope this was helpful to you.