I remember seeing a photo a while ago (on either this forum or the old one), taken inside a school building, at the intersection of the old and new wings. In the new wing, there was an electronic horn/strobe (a Wheelock NS, I think). But in the old wing, you could see a red Federal Signal siren on the wall. I looked to see if the photo was still here, but to no avail.
But still I wondered whether they could have actually been fire alarms. Then, I figured since this was a siren-related question, to search on the AirRaidSirens forums to see if anyone there mentioned them. Turns out, I found a post saying that schools in Oregon that were built during the height of the Cold War (1940’s-1960’s) were often equipped with Federal Model A’s, and they were used as both fire alarms and air raid alarms. Even more interesting - they said some were still in use!