Mann was elected to the legislature in 1827 and in that body was active in the interests of education public charities and laws for the suppression of intemperance and lotteries. In 1848 after serving as Secretary of the Massachusetts State Board of Education since its creation he was elected to the US House of Representatives. After their enactment he was appointed one of the editors of the work and prepared its marginal notes and its.
As a politician he served in the Massachusetts House of Representatives from 1827 to 1833. Mann has been credited by educational historians as the "Father of the Common School Movement". He served in the Massachusetts Senate from 1834 to 1837.