Hii,

Yes, of course you can take coaching for SSR and AA exam after your 12th exams. This exam is conducted twice in a year one in the month of June or July and the second one in the month of November or December. The syllabus is based on your 12th standard topics only. You have to do self study also and with proper time management and hard work you'll clear this exam.

Hope this helps.

All the best!!