- You may be looking for Room 4B, location of Coal Hill Chess Club.
Class 4B was a class in Coal Hill School.
In a delirium induced by a malfunction in The Doctor's TARDIS, Barbara Wright excused herself from having fallen asleep (she had really been knocked unconscious) on account of having had a busy day, including a difficult period teaching Class 4B about the American Civil War, which had instead resulted in an ink pellet battle. (PROSE: The Edge of Destruction)
Clara Oswald once taught Class 4B on a miserable wet Monday morning. (COMIC: Terrorformer)