Hired to teach in the State of São Paulo, she moved to Piracicaba where from 1882 to 1889 she taught science, developed the curriculum, and enhanced the reputation of the Colégio Piracicabano [pt].

Opening her own practice after she resigned from the Maternity Hospital, she operated a dispensary for the poor and immigrant communities, while continuing to see paying patients.

[3] Upon receiving her certification, Rennotte accepted a post in Mannheim, Germany, where she taught French language courses for three years.

Championing co-education and gender equality, it offered a well-rounded curriculum, including courses in languages, literature, mathematics, philosophy, and natural and physical sciences.

[13][14] Rennotte rejected the method of memorization previously used in Brazilian schools, instead requiring her students to give reasoned and complete answers to questions.

[15] Though the methods of the Colégio Piracicabano had the support of abolitionists, masons, and progressive politicians like Prudente Morais Barros and his brother, Manuel, there were anti-liberal and ultramontanist factions which aggressively opposed the school.

In 1883, the Sisters of St. Joseph, who operated the Colégio de Nossa Senhora do Patrocínio (Our Lady of Patronage College) in Itu, began a campaign to discredit the move away from traditional education for women.

[14] Watts acted as the administrator of the school, while in annual reports to the Methodist Woman's Missionary Society, Rennotte was given much of the credit for directing the curricula and enhancing the reputation of the Colégio Piracicabano.

[18] At the end of the 1886 term, Rennotte went abroad to study new teaching methods in the United States and France, securing textbooks and other materials for her science classes.

The state legislature rejected the report, allowing the school to continue,[19] and spurring Rennotte to begin offering night classes in chemistry and physics, open to any citizen who wanted to take part.

[20] In 1888, Rennotte began collaborating with Josefina Álvares de Azevedo, founder of the new feminist journal, A Família (The Family).

[14][2] She enrolled in the Woman's Medical College of Pennsylvania in Philadelphia to study medicine,[7][14] having received scholarship funds authorized by Prudente Morais Barros, governor-elect of the state of São Paulo.

[27] Rennotte opened a clinic in her home near the Praça da Sé (Square of the Holy See), from which she dispensed medicines to the poor and immigrant communities.

[30] In 1901, she was admitted as a member of the São Paulo branch of the Brazilian Historic and Geographic Institute[31] and four years later became a partner in the Associação Médica Beneficente (Benevolent Medical Association) operated by Arnaldo Vieira de Carvalho [pt],[32] one of Brazil's most renowned physicians of the period.

[34] In 1906, Rennotte conducted research with Vieira de Carvalho at the Surgery of the Santa Casa da Misericórdia on the effects of chloroform as an anesthesthetic.

Though the convalescent home was never realized, she began a campaign asking for students and well-to-do citizens of São Paulo to donate a tostão [pt] (penny) per month to the cause.

[35] During World War I, Rennotte trained Red Cross volunteers and during the 1918 influenza pandemic traveled throughout the state of São Paulo providing medical and humanitarian aid.

[36][38] As part of a South American tour, Carrie Chapman Catt attended the Congress and then went to São Paulo with Rennotte to help her found the Aliança Paulista pelo Sufrágio Feminino (Paulistan Alliance for Women's Suffrage).