I believe the return actually lists them as "Male Arsenal Cadets," and shows their occupations as "Cadet at Arsenal Academy." The Arsenal Academy was established by the state in Columbia along with the Citadel Academy in Charleston in 1842. It served as a preparatory school for the Citadel, and cadets who successfully completed their first year (i.e., as 4th classmen), could transfer to the Citadel to complete their studies. Most of the Arsenal's buildings were destroyed by Federal troops in 1865, and the institution was never reopened. The officers quarters building survived, and is now the Governor's Mansion.

Hope this helps.