Room 2 is Mr Chambers' office, as he is a Head of Year (Year 10). This room is wedged between Room 1 and Room 3, and has a door to Room 1 for no particular reason, like most of the rooms on the balcony.
As this room belongs to Mr Chambers, it is dubbed as the Chambers of Secrets. In this room however, you won't find a homicidal snake but rather a number of drawers, files, and filing cabinets - which one may argue is even more scary.