Usually only carried in ships- of-the-line, the primary task of the schoolmaster was to teach the midshipmen mathematics,trigonometry and theoretical navigation. Before being accepted into the navy, candidates for the postition of schoolmaster were examined by representatives of Trinity House at Deptford Strond to prove their ability to perform these duties. The emphasis, naturally, was placed on navigation. Besides teaching potential officers, schoolmasters were also encouraged, according to Admiralty Regulations and Instructions, to teach all of the youths on the ship in reading and writing.
A Schoolmaster with Midshipmen and naval cadets. He teachs them how to use a sextant, c. 1890 (x)
On all other ships below the rank of a ship of the line, the captain took over the teaching, whereby he concentrated only on the midshipmen. Having no specific status, most schoolmasters messed with the midshipmen and found their own place to berth, although in some ships a schoolmaster may have been lucky enough to have been given a cabin, as was the case with the chaplain within the gun room.
Interestingly, his rank status is not entirely clear. Actually, he was counted as a warrant officer, but it seems that he ranked more among the petty officers, and was paid the same as Midshipman,