Yeah! You can take drop after 12 for the NDA examination, provided you should keep in mind about the parameters important such as age. If your age gets over the limit then you aren't eligible for the examination. So be aware regarding this.

The basic eligibility criteria for the NDA examination is :

Nationality - Indian

Age limit - 16.5 to 19.5 years

Educational Qualification - Passed 12th standard with maths and physics

To know more about NDA visit the link below:

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

I hope this answer helps. All the very best for your future endeavors!