Some might say (or even make video essays on how) Mean Girls is already a loose adaptation of the tragedy and even references the play to acknowledge intended parallels. So you could say this is an unnecessary idea. But that's like arguing that we didn't need She's the Man because Just One of the Guys already existed. Okay, so maybe we really didn't. But a more literal translation of Julius Caesar is still a good idea. You could give it a student council setting, though not in a way that would make it too similar to Election. Or, if that's too obvious, set it amidst some high school sport, like both She's the Man and the Othello-based O did.
But should the famous assassination scene still involve a murder in the contemporary version? Even without the untimeliness of school shooting (O was shelved for two and a half years because of the Columbine tragedy), films depicting teens killing other teens, especially inside of a high school, tend to be frowned upon by many Americans these days (even in slasher flicks, I think). Maybe in the modernization "Jules Caesar" (or Julie) is merely arrested or somehow dethroned without need of a dagger. The line "et tu Brute" would still apply in some less-violent scenario.Whatever the ending, it'd be neat to see Stiles appear as a teacher in this.
Let me know how you would update Julius Caesar as a high school movie and how faithful you think it could be.