In 1994, while teaching at Bell High School in Bell, California, Foster was a public advocate of Proposition 187, a California ballot initiative to deny government programs of social services, health care, and public education to illegal immigrants. Her position was extremely unpopular at the school where she taught, which was 90 percent Hispanic. In 1996, after she argued on PBS's "MacNeil/Lehrer NewsHour" that illegal immigration was responsible for the low quality of Los Angeles schools, some of her colleagues at the school condemned her in an open letter. Two days later, she attended an anti-illegal-immigration rally where several of her supporters were attacked by members of the Progressive Labor Party, who allegedly wanted to harm Foster herself. Shortly thereafter, she left her job, which she calls a necessity resulting from her treatment at work. She went on speaking tours for the John Birch Society and took workers' compensation for an undisclosed mental disorder—which she describes as "stress" and "anxiety"—until her official retirement as a teacher in 1998.