My building now uses flex scheduling for library access so whether or not to stay with my students is not an even an option. I have worked in an elementary setting where my students went to the library every two weeks. It never occurred to me to leave my students in the library. Generally, students behave better when their own teacher is present. One hour every two weeks is simply not enough time for a teacher-librarian to establish that relationship. Of course, an LMS will have classroom management skills but I would not want her/him to be focused on management or discipline instead of the content and skills of the lesson. I agree with Jessica and her principal that this should be required of teachers.
That being said, her problem is one I do not envy. Teachers, I know this because I am one, tend to resist change. We, who should constantly be trying to improve, like having things "just so." We don't get a whole lot of personal time so taking any of that time will meet with resistance. Jessica has the support of her administration, which is ultimately important. She also says she will make her expectations very clear. This is a good idea. When it is presented as "this is our goal," "I will do this," "you do this," can't very well be argued. Of course, teachers will argue anyway, but they will eventually run out of steam and start using the time productively.