Many, I would assume. The HS has over 2,000 students.
I wonder if attendance records could be searched and narrowed down. Perhaps look at all absentees/late students that are associated with Holly's son, the boyfriend's son (I believe the boys attend the same high school but I might be mistaken) and/or students that live in the vicinity of the bus stop that Holly dropped her son off at, those who would physically see them and know that Holly was not at home during that time period.
Also, I've wondered-did Holly *always* go back home after dropping off her son? It seems kind of close time-wise. If she dropped her son off daily at 6:30, but left for work at 7am, it would seem likely that she'd sometimes just go straight to work from there, perhaps getting a coffee, cigarettes, or a lunch like so many of us do daily on our way to work. Did she frequently not go back home? I'm wondering if she was expected to be gone, so someone *She Knows*broke in, expecting her to be gone, and she came back and surprised them. Being that the trailer, which is a possible homicide scene, was broken into at a later date, this leads me to believe that there's at least one not so very smart person out there. If she knew the person, and could really get them into trouble if she called the police, some bad stuff may have gone down.
Perhaps a search of school attendance records with particular attention being paid to those who:
A. Lived near Holly
B. Know either her son or the boyfriend's son and may have knowledge of Holly's home and routine, or
C. Have a prior criminal history within the juvenile system, such as burglary, or those who may still be on probation and would be in very deep doo-doo if caught again.