After two years at Bideford he married Miss Benson in the Baptist Chapel at Biggleswade, her home town, and three weeks later they were on their way to South Australia, along with his parents, aboard the ship Albemarle, 704 tons, J. F. Trivet, master, arriving at Port Adelaide on 16 March 1852.
They expected to be greeted by Mitton's brothers Josiah and Edward, who had emigrated earlier, but they were away in the goldfields of Victoria with thousands of others, leaving the streets empty of healthy men; his sister and her husband had left for Western Australia.
They remained on the goldfields for about five months, and when Mitton returned to South Australia in March, 1853, he opened a school at Bowden, near the railway station.
The magazine failed amid a barrage of criticism and ridicule, and the Association disbanded, but Mitton later had the satisfaction of seeing State education adopting many of their proposals.
In 1866 he moved the school to premises in Stephens Place, previously occupied by Adelaide Educational Institution, naming it Rundle Street Grammar.