We had positive control measures on ours. Only one instructor and student at a time and unless you had eyes on both coming out no one entered for any reason. Before entering with a student, all staff and students were positively located by the instructor going in. We brought no more than six students to the shoot house at a time, with three instructors.
Our local range has a small shoot house for IDPA/USPSA matches that remains locked except for matches with only the MDs and club BOD having a key. The RO for that stage is responsible for being the last person out after a run is completed and no one is allowed past the start line, about twenty feet around the berm, unless with the RO.