My former middle school probably had my favorite system of all the schools I’ve gone to.
The school was divided up into three areas, first, there was the original part from the 60s. This contained two wings of classrooms, a cafeteria (that was also being used as an auditorium at the time), a gym, and all the main offices. They had Simplex 4903-9236 horn/strobes in the hallways, science rooms, and one in the cafeteria, gym, and one in each of the locker rooms. There were Siemens U-MHU-MCS horn/strobes for all of the classrooms, as well as additional ones in the cafeteria, gym, and locker rooms. I do not know what the original system was, but I believe the new system was a Siemens MXL.
There was a newer wing that was added on to in the 80s. This addition included dozens of classrooms and a new auditorium. The original alarms were on 2903 light plates which were in various places throughout the hallways. The alarms in this area were entirely comprised of Siemens U-MHU-MCS horn/strobes, which were installed directly onto the 2903 light plates, and more were added in the classrooms.
The newest wing from the 2000s added even more classrooms and a second gym. This area had all Simplex TrueAlerts.
All of the initiating devices were Siemens throughout most of the building. In the newest wing, they had Simplex pull stations, but they still had Siemens detectors which was interesting.