In March 1904, a 5.1 magnitude earthquake hit Eastport, Maine. Most earthquakes in Maine are so small that people don't notice them, though minor quakes are registered at regular intervals.
In Eastport, there were no serious consequences of the earthquake. Some chimneys toppled, but there was no structural damage to speak of; no people were injured - at worst, a few heartbeats had skipped.
Several miles away, in Kingsmouth, the effects of the quake were graver.
In town, a few windows shattered, bottles and cans fell from their shelves and people could feel trembling in the ground. In an otherwise sleepy town, it was an exciting event, but, on the surface, there was nothing newsworthy about it. A local reporter learned that Innsmouth Academy had suffered some structural damage and had to temporarily close, but for a building that old, this seemed no surprise. The highly private and enclosed institution didn't comment any further, and the reporter soon lost interest.
The untold truth is that the school was severely affected by the earthquake. Several buildings collapsed, killing forty-three people; thirty-nine of them children between 12 and 16 years old. No one could have saved them - death was inevitable. They were crushed under the weight of falling bricks and stones or skewered by splintered wood. Some died instantly and some endured hours of pain and fear before the last darkness finally embraced them.
More than a week passed before all the victims could be found in the rubble. Numerous bodies were difficult to identify because of massive trauma to the head. The structural damage to the academy was so complete that the school was forced to close for two years while rebuilding.
The benefactors of Innsmouth Academy, the powerful Illuminati, kept the tragedy top secret. Through use of potent magic charms and spells, they made sure the citizens of Kingsmouth didn't know how badly damaged the school was. Senior magi clouded people's minds and created an illusion that the school grounds looked normal. The citizens had no reason to doubt what they saw.
The full truth was even hidden from the secret world. Like any other faction, the Illuminati dislike losing face and would never admit they had failed keeping the school children safe - that would make them look weak and unprepared.
When news of the school's destruction reached the other secret factions, it was accompanied with claims that the earthquake had been a dark magic assault - that the real epicentre of the earthquake was right beneath the school. Further, it was claimed that the attackers were able to confine its full effect to a very small radius - just within the school's walls. Then, to cover their tracks, they invoked a smaller quake in Eastport.
Careful investigation found that the quake was indeed provoked, which meant that the students and teachers at Innsmouth were murdered. The secret world was uniformly horrified - killing children is a cardinal sin all factions take exception to. As much as history has been filled with fighting and even outright war between the organisations, none of them aim to hurt innocents, and least of all children. Everyone wanted to find the attacker.
Only an exceptionally powerful magus could hope to achieve the potency required to create earthquakes. In 1904, all major factions had such powerful magi among them. The Illuminati vigorously accused everyone else, but they all strongly denied having any connection to the murders.
Eventually, evidence pointed to the Templars, who persisted in their innocence. Ancient tension and animosity between the two powerhouses flared up and the Illuminati cried out for justice. The Council of Venice warned the Templars, others turned their backs on them. Finally, the London-based faction couldn't leave the allegations floating, and started their own investigation.
The Templars then discovered the truth themselves - a splinter cell of their organisation had planned and executed the attack. They found the inaction and tolerance of their own faction unbearable, and attacked the school as a powerful statement of their ability and intent.
They targeted Innsmouth Academy because it was one of the Illuminati's strongholds and a nesting place for future magi who would surely use their powers to destroy the secret world and all within it. All the members were found and discretely dealt with by their own faction.
Within the secret world, the two absolute harshest punishments are death and the stripping of powers. Often, one goes hand in hand with the other. The leader of the radicals was hanged and his body cremated. The remaining members were cursed - rendered unable to use their spells and magical abilities - then thrown out on the streets. Without any real skills and unable to use their magic, the convicted soon succumbed to merciless reality and were never heard from again. Self-justice in the secret world is harsh.
Innsmouth Academy had thereafter set up a great many defences, all aimed to protect the students, the school and the countless secrets within. Only the foulest and darkest of magic would be able to crush Innsmouth again - yet now, once more, it lies in ruin, devastated and emptied by the recent events.