Other than that, the producers still aren't totally sure what to do about Bart's lack of a teacher:
So who will replace Mrs. Kabrappel [sic.] in the fourth-grade classroom? For the time being, no one. The rest of this season's episodes -- which already have been completed -- do not involve Bart with his teacher.
It appears they've already been removing her from classroom scenes. There's a recent episode where a still image of Groundskeeper Willie is just pasted in the background of a scene (I'm pretty sure he doesn't blink).
As for season 26, "we have some ideas," says Jean. "It's also possible both given the way the show works and the state of public schools there won't be a permanent teacher. We can get some great guest stars here and there before we settle on somebody. We're looking at it from different angles."So, basically it'll be like the post-Steve Carell episodes of The Office, then. Great!
While my preference would be for the show to cease production immediately, my worthless, hacky suggestion is to just have Principal Skinner take over. It'd give the show more chances to focus on his adversarial relationship with Bart and, as a bonus, isolate him from his mother, who's easily my least favorite character. Meanwhile, Superintendent Chalmers would naturally become principal, since he's already at the school all the time anyway.
Either that, or it's finally time for Nameless Ponytail Teacher to step into the spotlight.