I've always had confidence....BUT mine might not count.
It's that quiet confidence...the type that doesn't care to impress anybody, lol
Not cocky....though american women love that (even when they lie about not liking it), so take that as you will.
as for school, I did well in things like literature, history, physics (the reading part)....math, statistics and labs always messed me up.
So yeah, my type of confidence isn't what you're looking for...IE., real confidence

Try to be loud and obnoxious and yes, try to treat people crappy...basically try your best to e a jerk but with tact, that's the type of confidence MOST people readily accept. If you're a jerk but you pay attention to them, they'll love you, if you're not and you mind your own business and couldn't care less to know them, they'll hate you for it.