In School and Out by Oliver Optic

The apartment to which Richard was shown was called "Barrack B. " There were ten rooms of this kind, known by the first ten letters of the alphabet, omitting J. Each barrack contained twenty narrow iron bedsteads, and no two boys were allowed to occupy the same bed. At the head of each barrack, there was an alcove large enough to contain the bed of the assistant teacher, who had charge of the pupils in the room. This apartment of the instructor was screened from the view of the boys by a curtain, so that he could see without being seen, when he desired to do so.

There was a small closet in the wall between every two beds, for the use of the boys, and Richard was directed to transfer the contents of his trunk to this receptacle, by Mr. Gault, the assistant teacher in charge of Barrack B. Richard opened the trunk, and then sat down upon the bed to wait until the instructor should retire, for he did not care to exhibit his wardrobe to a stranger.