After earning her doctorate, Lehr stayed at her alma mater, Bryn Mawr, as an instructor; she was promoted to associate lecturer in 1929, assistant professor in 1935, and associate professor in 1937. In 1955, she was made a full professor. While at Bryn Mawr, she had temporary or honorary appointments at several other universities. At Johns Hopkins University, she was an honorary fellow from 1931 to 1932; she was also a visiting fellow at Princeton University from 1956 to 1957. In 1958 she was given a traveling lectureship by the Mathematical Association of America and the National Science Foundation, and was funded to give lectures across the country. She also worked with the MAA and NBC to produce educational films about mathematics, and conducted a televised lecture course on mathematics in 1953 and 1954. While at Princeton, and for the following decade, she was a member of the Woodrow Wilson Fellowship Award committee.
