Dear Candidate,

To be eligible for NDA Test, you must be either appearing in 12th class or had passed the 12th class. And also, your age must lie between 16.5-19.5 years. If you satisfy this criteria, only then you are eligible to give the NDA Exam. So as per calculation you have 2 chances of NDA Exam, when you will be in your 12th class. And  1-2 chances after completing your 12th class.

Hope it helps you.