Hi.

NTSE exams are conducted by the state education sector.

If your school is not affiliated, no worries. You can fill up the form online
( https://school.careers360.com/articles/ntse-application-form ) but you have to submit it offline and for that you may need the help of your school. But DO not worry , contact office and I am sure they will help you.

Also check for the eligiblity criteria which you can find at https://school.careers360.com/articles/ntse-eligibility-criteria

The other help you will need from your school will be the principal's signature on the admit card.

WIsh you all the best.