One thing we do not know, is how much older the males involved in criminal activity they were though. One of my sisters went through some stuff when she was 14, and had a summer where she basically refused to come home. Her boyfriend's mom at the time was contributing to it, long story, but things happen. Middle class family, she ran track, was an honor student, just decided she was in love with a guy a few years older who was mixed up in stuff. I believe the boyfriend was 16, but I'm sure he associated with people in their 20s, so by default, so did she. His mother absolutely associated with criminal elements. My point is just to demonstrate how easily this could happen. All it would take is one link, and bam.
Also, in Texas, at least now, you can be certified as an adult for serious crimes at 14. They house the under 18 yos separately. I actually found mention of moving these "youthful offenders" who are classified as adults to the Ellis Unit while looking for info about this case. It was done recently though. I do not believe there were teens there at the time of Sherri's murder.