First one was the one in Rio de Janeiro. The one that I study at is in Curitiba and as stated, its a military school, but there's a way to join in it by being civilian, you do a Math test and if you pass it you do the Portuguese test. When I did it there were only 50 spots for people out of 2.000 to 3.000 contestants, so I guess only the smart get in it without being the son of an army guy or something like that.
You should dress up as an arab, and go to an airport or some other public place and see if you get pulled aside.