I'm getting tested, but I don't know if i'll p the hair test.?

i'm not trying to be a smart ***, i'm being dead serious. i'm getting my license in december. my parents want to drug test me, and i'm pretty sure i'm not clean. i'm in 11th grade, cut me some slack. the last time i was actually high was like a month and a half ago. and then i took a hit out of a bowl about a 3 weeks ago, but i stopped after the one hit. i wasn't high or anything. and then last week i took another hit, but i quickly changed my mind and didn't even inhale. i'm well aware that thc is fat soluble, and i'm very skinny. i don't have a clue as to why i actually decided to smoke those two last times, but regardless, now i'm facing the consequences. i don't know when exactly they wanna test me, i can't get my license until december 26th, so i'm hoping they wait until after that, because i should be cleaned out. They wanna take a piece of my hair, and i was reading something that said traces can be found in your hair indefinitely. is that true or not? if it is, is there anything i can do to clean myself out?