The newest member of staff they've introduced is Simon Trent, the school's resident drama teacher. He was first mentioned several times in issue #1 (October 2014) in dialogue, on a sign, and on a poster for a movie called "House of Secrets" (which he starred in with Basil Karlo, aka Clayface), but his first actual appearance was in issue #4 (January 2015). He even says he has "experience playing a ghost"!
Simon Trent, as I'm sure you know, was featured in an episode of Batman: The Animated Series called "Beware The Gray Ghost" (1992). In the episode, Simon Trent is an actor who played a superhero called The Gray Ghost in an old tv show Bruce Wayne watched when he was a kid. The Gray Ghost was part of what inspired Bruce to be Batman, but over the years the show faded into obscurity. In an ironic but terrible - and all too real - situation, the show is too obscure for Trent to live on the royalties or props sales anymore, yet still well known enough to have Trent still associated with the role, and therefore not being able to get any others. Nevertheless, Trent teams up with Batman to track down a bomber who's basing his crimes on an old Gray Ghost episode, which leads to a surge in the show's popularity and things turn out ok for Trent in the end.
Although this is Simon Trent's first appearance, the "Gray Ghost" persona - and the Mad Bomber - has appeared as well, which I talk about in the Batman The Animated Series Super Post.