Answer by taking a quote from the following article:

Madalyn Murray O'Hair (nee Mays; April 13, 1919 - September 29, 1995), was an American activist, founder of American Atheists, and the organization's president from 1963 to 1986. She created the first issues of American Atheist Magazine. O'Hair is best known for the Murray v. Curlett lawsuit, which led to a landmark Supreme Court ruling ending official Bible-reading in American public schools in 1963. That case came just one year after the Supreme Court prohibited officially sponsored prayer in schools in Engel v. Vitale.

Murray filed a lawsuit against the Baltimore City Public School System (Murray v. Curlett) in 1960 in which she asserted that it was unconstitutional for her son William to be required to participate in Bible readings at Baltimore public schools. In this litigation, she stated that her son's refusal to partake in the Bible readings had resulted in bullying being directed against him by classmates and that administrators condoned it.  After consolidation with Abington School District v. Schempp, the lawsuit reached the Supreme Court of the United States in 1963. The Court voted 8-1 in Schempp's favor, which effectively banned mandatory Bible verse recitation at public schools in the United States. Prayer in schools other than Bible-readings had already been ended in 1962 by the Court's ruling in Engel v. Vitale.  O'Hair filed a lawsuit with the National Aeronautics and Space Administration (NASA) in regard to the Apollo 8 Genesis reading. The case was rejected by the U.S. Supreme Court for lack of jurisdiction. The impact of the suit was limited: Although NASA asked Buzz Aldrin to refrain from quoting the Bible in the Apollo 11 mission, he was allowed to conduct the first Communion service in space.  O'Hair appeared on The Phil Donahue Show several times, including the first episode in 1967, following which Phil Donahue said O'Hair was unpleasant and had mocked him off camera for being a Catholic, although after O'Hair's death, Donahue described her message of atheism as "very important". She appeared on the show again in March 1970 to debate Preacher Bob Harrington, "The Chaplain of Bourbon Street".  O'Hair endorsed Jimmy Carter in the 1976 presidential election because of Carter's opposition to mandatory school prayer, his support for sex education in public schools, and his stance on ecological matters.

what causes what O'Hair active in?
she stated that her son's refusal to partake in the Bible readings had resulted in bullying being directed against him by classmates and that administrators condoned it.