What does mean "Which I guess it pretty much is"?
The full text is: " We called the bus the Singleberry Express and sometimes the Singlebus, although Heller had once commented, “That thing looks like it’s taking mentally handicapped students to choir camp. Which I guess it pretty much is.”"

Question

Answer

The writer/author is agreeing with 'Heller' saying that what he said is correct. :)

Ne manquez pas cette occasion d'apprendre une langue depuis chez vous. Découvrez notre sélection de professeurs de langues expérimentés et inscrivez-vous dès maintenant à votre premier cours !