When Ms. Li is compelled to fire one of her substitutes for being a pedophile, she is forced to find a replacement - and she finds Miss Darlene, AKA Daria Morgendorffer.

Daria takes on the moniker of Miss Darlene because her history substitute called her that, saying that "Daria" was a hippie name and that "Darlene" was much prettier.

Quinn is naturally mortified that Daria is teaching her class. Fortunately, a fair number of her classmates are too thick to realize that Miss Darlene is actually Daria.

Miss Darlene takes the class through Romeo and Juliet, having the three J's read a good part of it. She refers to each of them as "Joey, Jeffy, or Jamie" indicating that she really doesn't see much of a difference between them. She then gives an essay test with a single question: What was Romeo and Juliet about?" Miss Darlene grades the tests based on how well the students think for themselves when answering, giving a high mark to Jeffy for defending his premise that Mercutio was homosexual - but giving Sandi a D-minus for writing that Leonardo DiCaprio took a swim in his clothes.

Presumably Miss Darlene taught other classes besides Quinn's Language Arts class, but we do not see her doing so. Her fellow students waste little time in hitting her up for excuse notes to get out of class, indicating that the fact that she is a teacher is no secret.