I believe the law has now been amended so that only babies may be dropped off, but before the amendment almost all of of children surrendered were 5 years old and older. And yes, many were teens.
I feel awful for the children, but I also feel terrible for these parents who were at their wit's end with these kids. A large percentage of the children had a history of mental health problems; some had behavioral issues. The parents didn't know how to handle them anymore, and they felt they had nowhere else to turn for support.
Most of the people I know really romanticize having children, and they never acknowledge how difficult, even tragic, it can be for some people. To me, Nebraska's story is a loud and clear message that parenthood isn't for everyone.