I want to join Indian Army.Please suggest me some good army school for class XI....

Better you do 10+2 in science stream from any good english medium institution and appear fro NDA examination or you can do Graduation and then appear for CDS exam

You can think of Services Preparatory Institute, Ahemadnagar(MH). Even joining RIMC could be a better option. They are fatories for sending boys for NDA. For you, after class XI, joining NDA is the as good as catching the first bus to fulfill your dream.

Basically all army school known as sainik school running by ministry of Defense govt of India. Admission on these school in Class VI & IX on entrance exam basis. You can Try for NDA after 10+2 or CDS after graduation or there also many opportunity after ENGG. recruitment drive published in newspaper

If you wish to join army so there is no need to do class XI from army school you can join army at any time after 10 there are various entry points and levels you need to decide your goals