In 1919, she returned to Germany on a Quaker war relief mission and was asked by her sister, who had founded a children's home, to help establish a school with it.

By the time Essinger closed Bunce Court in 1948, she had taught and cared for over 900 children, most of whom called her Tante ("Aunt") Anna, or TA, for short.

Her task was to convince mayors, teachers and school rectors to set up kitchens so that children could have a hot meal once a day.

[2] In 1912, using her dowry, her sister, Klara Weimersheimer, founded an orphanage in Herrlingen, where she cared for problem children,[6] as well as those mentally unstable and disabled.

[11] She ran Landschulheim Herrlingen like a Montessori program,[2] placing high value on communal living, mutual respect and a shared sense of responsibility for the school.

In the evening, Anna Essinger read a story and then gave each child a "good night kiss" before sending them off to bed.

A 1927 report by the Ministry of Science, Art and Education (Ministerium für Wissenschaft, Kunst und Volksbildung) described Essinger as "extremely competent" and her teaching as "skillful, fresh and stimulating".

[9] Adolf Hitler's rise to power and the growing Nazi threat were viewed ominously by Essinger, who immediately went about quietly boycotting the Third Reich.

[16] An old manor house dating from the time of Henry VIII was found in the village of Otterden near Faversham, in the County of Kent.

Funds were meager, so work on the property was done by the staff and pupils, causing British education inspectors to view the new school unfavorably at the outset.

[2] After Kristallnacht, on 9–10 November 1938, Essinger was asked to set up a reception camp in Dovercourt for 10,000 German children who would be arriving on the Kindertransports.

[17] Essinger, then nearly 60 years old, worked with three teachers, her cook and six of the older pupils to establish the camp, taking some of them into her school.

Her eyesight was failing, but more significantly, the last children to arrive at her school were Nazi concentration camp survivors who no longer knew what normal life was like, and sometimes found it very difficult to adjust to.

After she closed her school, Essinger spent her remaining years living at Bunce Court, and maintained correspondence with her former pupils.

In July 2007, the original Bunce Court school bell was retrieved from California, where it had been saved and stored by Ernst Weinberg, a former pupil, and was reinstalled on top of the schoolhouse.

In 2004, the Oxford Dictionary of National Biography added an entry for Essinger,[21][22] unusual for someone who became a naturalized British citizen late in life.

The celebration for Essinger lasted a week and was attended by family members from the United Kingdom and Israel, as well as Germany; and former students.