Hello Aspirant,

To join National Defence Academy a candidate must appear in the entrance exam conducted by Union Public Service Commission, twice a year, normally in month of March and August in class 12th . Candidate must be a unmarried male. To join NDA one must pass written followed by SSB, medicals and finally to be in merit list. Written exam consists of 2 papers 1st mathematics(300) and 2nd is  of general ability test(600=200+400).Mathematics paper consists of topics from  11th and 12th standard mathematics while 2nd paper have English(200) and G.K.(400) as its part A and part B. I'll recommend you to go through your 11th and 12th syllabus thoroughly and practice past year papers. Also you must spend some time for physical fitness.

All the best

You can appear for the NDA exam while you are in your class 12 . If you do get selected,you will have to clear class 12 and get the marksheet. The preparation you need will be in basic class 10,11 mathematics and reasoning and logical thinking. Also keep yourself upto date with current affairs