 Though just 20 years of age he was made headmaster of the Sydney public school on 1 July 1827 when his father resigned.He had already made a reputation as a teacher and shortly afterwards, when a number of public school teachers from the country were brought into Sydney for training, Cape was given charge of them as he was considered the only qualified person available.In 1829 he opened a private school in King Street, Sydney, and when the Sydney College was founded in 1835 he transferred his own pupils there on being appointed headmaster.