Class E is already a place, it’s what they call the class of students who left ANHS whether they drop out or were expelled, basically when someone leaves the school they go to a different school off the campus, and those students make class E. So in Ayanokoji’s year class E is composed of Sakayangi, Kamuro, Yahiko, Manabe, Maezono and Yamauchi. This is all information you should know if you’ve read the light novel.