Hello Yash,

congratulations on your decision to join the NDA.

The eligibility criteria says that you should have passed your 10+2 from a recognised board. As open schools are also a national board, it is aceepted as ling as you have the paasing certificate from NIOS.

For more details of the eligibility criteria follow the link below :

https://competition.careers360.com/articles/nda-eligibility-criteria/amp

Hope this helps.

All the best!