That’s true.
The ramp up in fire safety probably came after the Our Lady of the Angels school fire, which occurred on December 1, 1958. The cause was arson. 95 people died: 92 students and 3 nuns. Many died from smoke inhalation when normal exit routes were cut off: this is why schools ALWAYS have an alternate exit plan; at least most do, unless they’re really old. Others from jumping out of two story windows in desperation; it was really 3 stories (as the school had a raised basement). Mind you, this is coming from Wikipedia, which depending on where you look may or may not be a reliable source. So don’t take my word for it if it’s an error.
But that’s my theory.
Also, keep in mind many schools have just as many pulls as others and no false alarms occur or barely any happen at all. Why? The answer: ramp ups in school security causes them to install video surveillance cameras. And lots of them are installed right near the fire alarm.