Hi Shivam ,

To get admission in class 9th in any particular school you have to apply there and give the entrance tests of the schools in which you wants to get the admission. 

For example - if you want admission in navodaya school then you have to give the navodaya school entrance test; 

if you want admission in kendriya vidhyalaya then you need to give its particular school entrance test and interviews; and so for any other school in which you want the admission. 

Also, prepare well for all subjects like- hindi,english,maths and science from your 8th class syllabus to get good marks.

Good luck.