In 1837 Mann was appointed secretary to the board of education. Through his post on the board he influenced the educational system not only of Massachusetts but of the entire United States. Although the board's powers were limited, it was able to affect public opinion regarding school problems and to create public support for increasing the pay of teachers and improving their training through the founding of state normal, or teacher-training, schools. In 1843 Mann visited Europe, where he studied educational conditions and methods. On his return he incurred the opposition of conservative American educators by championing such features of European education as the abolition of corporal punishment. He was also opposed by church officials for advocating nonsectarian education. These attacks, however, only served to arouse public sentiment for reform of the public school system.
Mann resigned as secretary of the Massachusetts board of education in 1848, when he was elected to the U.S. House of Representatives to fill a vacancy caused by the death of John Quincy Adams. He served until 1853, when he became president of Antioch College (now Antioch University), a newly founded nonsectarian, coeducational institution at Yellow Springs, Ohio. Mann held this post until his death. His 12 annual reports written when he was secretary to the Massachusetts board of education are a record of ideas on meeting educational needs by a man who strongly influenced the evolution of modern education.