Are you talking about being kicked out of your parent's house if they knew you were poly or thinking about trying poly? Are you concerned about abuse?
If so, is there a way for you to move out? Do you support yourself?
Finally, if that is the possibility you face, I will give you the same advice Dan Savage gives to young LGBT folks who live with unsupportive parents. Do what you have to do to survive, to graduate (college in your case), so you can later get the fuck out and live happy and open on your own. That means lie if necessary, be closeted. I usually recommend the path of openness and honesty but this is the exception - where you fear for your housing and safety.
Good luck. Be careful.