I agree it is a bad situation but if your choices are either live a lie or get thrown out of the house without any financial support, the easy answer is live the lie.
I did for many years, I was determined to get a college education and to be financial independent from my parents. It would buy me the right to make my own decisions and live my life the way I wanted without the ramifications from my family.
Once I got my education I got outta the "troof" as fast as possible and I have never regreted my choice.
Try not to judge these kids too harshly. They are just trying to survive in a tottally unhealthy environment.