Banshee's are omens of death. According to legend they're women who have died and are watching their families from beyond however this isn't true. Banshees are as alive as any other supernatural creature is. And about as close to human as they are too even if they are able to pass as human many still choose to live at the Academy due to their abilities making them a target of bullying in the outside world.
Banshee's are Harbinger's of death. Most are born this way, a trait passed down the generations however some have been cursed with it. A banshee's power is unpredictable in how it will manifest, some turn up moments after a death has occurred it's happened other's know it's going to happen hours or days before hand. The thing they all have in common however is their ability to hear the dead, however they can only do this before a living person's death. Typically a banshee's power manifests in a scream before or a particularly violent death.