Who was behind the murders at Scholomance that occurred during Ophelia's junior year in the novel, The Golden Enclaves?

While Ophelia was a junior at the Scholomance, she killed a whole senior class in the graduation hall and blamed it on a group of different maleficers who she helped hunt down and kill. Still, no one suspected Ophelia of being the evil maleficer behind all of the deaths.

This is a half-correct answer to an incorrect question. The mass murder happened during Gwen Higgins' junior year in the Scholomance; by this time Ophelia Rhys-Lake, the perpetrator, was graduated, married, and on the school board of directors.

Orion's mum is significantly older than El's.