Eternal Algebra Class

Eternal Algebra Class with Four (or its official acronym, EXIT, even though the acronym spells out Eternal Xalgebra Iclass Twithfour), or simply Eternal Algebra Class (mentioned by Balloony), is where contestants go after they are eliminated in Battle for BFDI.

In EXIT, characters seemingly have to endure endless lessons and worksheets about algebra.

Four also shows suspicion about how Balloony knows about EXIT, and it is also unknown why Eternal Algebra Class's existence shouldn't be known, more or less as a secret.

Until Enter the Exit, Eternal Algebra Class had not been seen onscreen, but it was finally revealed.