The daughter of a Unitarian minister, she founded a ragged school and reformatories, bringing previously unavailable educational opportunities to poor children and young offenders in Bristol.

He established a boarding school at Great George Street, Brandon Hill, which was run by his wife and daughters,[3][4] where Mary studied the sciences, mathematics, Greek and Latin.

[10] He is said to have directly inspired her start on the path of social reform, partly by a chance remark made when walking with Carpenter through a slum district of Bristol.

[11] In 1835 she helped organise a "Working and Visiting Society", in the slums around Lewin's Mead, of which she remained secretary for nearly twenty years.

[13] The purposes of such societies were to visit the poor and raise funds from the emerging middle classes to alleviate poverty and improve education.

[19] A bill had been introduced into Parliament "to make provision for the better education of children in manufacturing districts", but it failed to pass due to nonconformist opposition as it was seen to give pre-eminence to the position of the Church of England.

[25] This book drew public attention to her work, and she began to communicate with leading educational and reformist thinkers and reformers.

[29] When Lady Byron died in 1860, Mary Carpenter was given a legacy to outright purchase the Red Lodge, including a cottage to be used for training the girls in domestic service.

12693/1-2) (online catalogue) present the earliest days at the Red Lodge transforming it from deserted house into functional school, including the discovery of a human foot in an outhouse.

[30] Carpenter's diaries also reveal the use of 'the cells' located in the cellar of the Red Lodge for disciplining "violent, refractory and noisy girls".

[33][28] In the same year, Carpenter was invited to give evidence to the House of Commons Select Committee on the Education of Destitute Children.

She condemned the "low Anglo Irish" as combining "the vices of the English in a large commercial town with their ... natural character in a very undesirable way.

She was particularly concerned that the lack of good female education led to a shortage of women teachers, nurses and prison attendants.

[30] She also participated in the inauguration of the Bengal Social Science Association,[39] and addressed a paper to the governor-general on proposals for female education, reformatory schools and improving the conditions of gaols.

[18] At the International Penal and Prison Congress in 1872 Carpenter read a paper on The Principles and Results of the English Reformatory and Certified Industrial Schools.

[18] Princess Alice of Hesse, who had become interested in social reform, invited her, along with Catherine Winkworth, to Darmstadt to help organise a Congress of Women Workers in 1872.

[44] She went on to Neuchâtel, Switzerland to study Louis Guillaume's prison system,[23] and in 1873 to America, where she met abolitionists such as William Lloyd Garrison and Frederick Douglass.

[12] Carpenter's campaigns for juvenile penal reform had a major influence on the development of a more enlightened regime for dealing with young offenders.