Not sure if you remember this case. Back in 2006, a 13-year-old boy named Thomas White reportedly brought a gun to his middle school. He fired one round into the ceiling, and he tried shooting a principal, only the gun jammed, police allege. He was certified to stand trial as an adult, despite being very young, and has been in custody ever since.
He's 16 now. He's being evaluated to see if he's mentally competent to stand trial. Last year, a judge ruled that he wasn't.
Meanwhile, he keeps getting closer and closer to the magic age of 17. Right now, if he's found guilty, he could be put in a juvenile program, get some schooling and counseling. After he hits 17, he must be put in an adult prison. (I remember another case from southeast Missouri, last year IIRC, and another kid, just turned 17, who was being sent to a max-security prison. He killed himself a few hours before they were going to make the transfer.)
I found a really thoughtful post by a Missouri blogger, The Heartland Diary of Betty B, that talks about White's case.