his mother, mary clancy, is feeling emotional about her >> i was just hoping i would not start crying in the classroom. parents launch their children into the world, eager to see what lies ahead. but for the families you will meet tonight, the joy they feel in this moment masks the terror and dread lurking just below the surface. >> i wake up every morning drenched in sweat and worried about what am i going to do about eric? >> reporter: when eric and nick leave school, they will lose the specialized help and structure they have had for most of their lives. and there is no equivalent state or federal support required to take over. parents of children with autism compare it to falling off a cliff. >> happy graduation, everything that we worked for, we are taking it away. and you will leap off the cliff into nothingness. right now the picture its nothingness. it is black. absolutely black. >> reporter: for the last three years, "dateline's" cameras chronicled the lives of the two families as they made this leap. >> i don't think i have ever been more terrified than i am >> reporter: we