What grade is Bart Simpson in?

It’s not often that a character from an animated sitcom causes a mania, but as "The Simpsons" gained popularity in the early ‘90s, Bart was largely featured as a protagonist in those early days — as well as featured on merch. It all led up to Bartmania, with as many as a million shirts featuring his likeness selling within a single day.

Bart was so big that Michael Jackson sang backup vocals for him on the novelty single, “Do the Bartman.” That’s right, MJ was backing up Bart, not the other way around. 

Besides telling people to eat his shorts, writing things on chalkboards, and generally causing mischief, Bart is also a student. Usually a poor student, but still, he is one. And with "The Simpsons" adhering to a floating timeline in which the characters never really age or change, he’s been in the same grade for all 35+ seasons. What grade is he in?

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