Kindergarten Teacher Wendy Wadsworth protests against Florida Bill SB6, which aimed to eliminate teacher tenure. Source: Tiffany Tompkins-Condie, www.brandenton.com, Apr. 15, 2010
Teacher tenure is the increasingly controversial form of job protection that public school teachers in 46 states receive after 1-5 years on the job.  An estimated 2.3 million teachers have tenure. 
Proponents of tenure argue that it protects teachers from being fired for personal or political reasons, and prevents the firing of experienced teachers to hire less expensive new teachers. They contend that since school administrators grant tenure, neither teachers nor teacher unions should be unfairly blamed for problems with the tenure system.
Opponents of tenure argue that this job protection makes the removal of poorly performing teachers so difficult and costly that most schools end up retaining their bad teachers. They contend that tenure encourages complacency among teachers who do not fear losing their jobs, and that tenure is no longer needed given current laws against job discrimination.
Prior to the introduction of teacher tenure, teachers were often fired for non-work related reasons. Teachers could be dismissed if a new political party took power or if a principal wanted to give jobs to his friends. Calls for special protections for teachers coincided with the women's suffrage movement and labor struggles during the late 19th century. The National Education Association issued a report in 1885 advocating for public school teachers to receive tenure to protect against political favoritism and discrimination based on gender and race. In 1886, Massachusetts became the first state to pass a pre-college tenure law.  When nearly 10,000 teachers arrived in Chicago for the 1887 NEA conference, teacher tenure was one of the main discussion topics. In 1909, New Jersey passed the first comprehensive K-12 tenure law in the US. Proponents of the teacher tenure law in New Jersey argued that it would attract more qualified teachers and eliminate political favoritism, while opponents warned that tenure would make it more difficult to remove ineffective teachers. 
After the Great Depression, teachers began to organize politically in order to receive funding and job protections.  Teachers unions negotiated for tenure clauses in their contracts with state and individual school districts. By 1940, 70% of K-12 public school teachers had job protections. In the mid-1950s, the number grew to over 80%. 
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Cover of the Mar. 15, 2010 issue of Newsweek Magazine Source: Eric Tipler, "Fire Teachers and Replace Jefferson with Aquinas? A Bizarre Week in Education," www.huffingtonpost.com, Mar. 16, 2010
Education and tenure reform became a national issue following the release of A Nation at Risk, a 1983 report of President Ronald Reagan's National Commission on Excellence in Education that found "the educational foundations of our society are presently being eroded by a rising tide of mediocrity that threatens our very future as a Nation and a people."  The report prompted states to look at reforming tenure, strengthening educational standards, and increasing the use of standardized tests.
Following the release of a 1985 report by the Illinois State Board of Education showing that only three tenured teachers were dismissed on average per year, the Illinois legislature changed their tenure laws to make it easier to dismiss under-performing teachers.  In the 18 years following these changes, only 39 tenured teachers were dismissed. 
In 2000, Georgia Governor Roy Barnes, a Democrat, successfully pushed a law through the legislature eliminating tenure for new teachers. Barnes told a joint session of the General Assembly, "Most of the time, tenure means a principal doesn't even try to dismiss a bad teacher because, even if the principal bucks the odds and succeeds, the cost in time and money is staggering."  When Barnes was up for reelection in 2002, teachers refused to support him, helping Sonny Perdue to become the first Republican Governor of Georgia since 1872.
California Governor Arnold Schwarzenegger took the issue of teacher tenure directly to the voters in a Nov. 8, 2005 special election. Proposition 74 called for the period of time before a teacher becomes tenured to be extended from two years to five years. In response, the California Teachers Association increased member fees by $60, raising $50 million to fight Proposition 74.  The proposition failed, receiving 45% of the vote. 
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Length of tenure, state by state Source: Stephen Sawchuk, "States Strive to Overhaul Teacher Tenure," www.edweek.org, Apr. 7, 2010
On July 24, 2009, President Barack Obama and Secretary of Education Arne Duncan announced the Race to the Top program which made available $4.35 billion in grants to "encourage and reward States that are creating the conditions for education innovation and reform."  Requirements for states to receive funding from the new federal program include adopting policies that take into account student achievement when evaluating teachers and having plans to remove "ineffective tenured and untenured teachers."
After failing to win Race from the Top funding, Colorado passed legislation in May of 2009 making it possible for teachers to lose their tenure status. Also in 2009, Ohio extended the period before a teacher becomes tenured from three years to seven.
Despite New York City Mayor Michael Bloomberg favoring "ending tenure as we know it," the United Federation of Teachers, with the largest political-action fund in New York City, has so far been able to protect tenure for teachers. New York is currently ineligible to receive Race to the Top funding because of an April 2008 law passed by the state legislature banning the use of student test data when making tenure decisions. 
Some changes to tenure have been made under the leadership of Joel Klein, Chancellor of New York City Public Schools. From 2002 when Klein was appointed by Mayor Bloomberg, until 2009, the percentage of third-year teachers not receiving tenure has risen from three percent to six, and the percentage of tenured teachers receiving unsatisfactory ratings increased from 1% to 1.8%. On June 28, 2010, the city’s "rubber rooms," where approximately 600 tenured teachers "accused of incompetence and wrongdoing” received a full salary to sit in a sparse room every day, were closed. 
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Joel Klein, Chancellor of New York Public Schools from Aug. 19, 2002 to Jan. 1 2011, discusses teacher tenure and school reform on ABC's The View. Source: "Klein: Time for the Reformation," www.nypost.com, Sep. 28, 2010)
A Feb. 11, 2010 LA Weekly investigation found that the Los Angeles Unified School District spent $3.5 million trying to fire seven under-performing teachers. On average, legal struggles to remove each teacher took five years and ended with four of the teachers being fired. Thirty-two other under-performing teachers were given an average of $50,000 by the district to quit. 
In 2008, DC Schools Chancellor Michelle Rhee proposed giving teachers the option of linking pay to performance in exchange for teachers giving up tenure. Union leadership refused to allow their membership to vote for the proposal that would allow teachers to earn up to $130,000 a year. When the DC teachers union allowed their membership to vote on the proposal in June of 2010, 80% of teachers voted in favor of it. The following month, Ms. Rhee fired 241 teachers and placed 737 teachers on notice for being "minimally effective."
On Sep, 24, 2010, the documentary Waiting for "Superman" brought the debate over teacher tenure and New York City's "rubber rooms" to the big screen. The documentary by the Academy Award-winning director of An Inconvenient Truth took a negative view of teacher tenure and teachers unions, prompting American Federation of Teachers President Randi Weingarten to call the film "unfair," "misleading," and potentially "dangerous." 
The New Jersey School Boards Association issued a white paper on Sep. 30, 2010 calling for an overhaul of the tenure process.  In his State of the State address on Jan. 11, 2011, New Jersey Gov. Chris Christie (R) said "the time to eliminate teacher tenure is now."  The New Jersey Education Association has proposed changes to teacher tenure such as using arbitrators instead of judges to hear dismissal cases, but it plans to fight the Governor over the elimination of tenure. 
Between Jan. and Aug. of 2011, 18 state legislatures modified their teacher tenure laws.  Many states chose to include teacher performance evaluations in their revised tenure legislation, and the Idaho legislature passed SB 1108 which phased out tenure for new teachers. In 2014, lawmakers in Kansas repealed a decades old law that provided tenure to teachers with at least three years-experience in a school district.  By 2017, four states required evidence of teacher effectiveness "to be the determinative factor" when granting tenure.  15 states required "some evidence of effectiveness to be considered," and a further 27 states and DC did "not require evidence of effectiveness to be considered," because "tenure is granted virtually automatically."  Four states did not offer tenure to K-12 teachers. 
On June 10, 2014 Los Angeles Superior Court Judge Rolf M. Treu ruled California's teacher tenure laws unconstitutional (Vergara v. California). The ruling targets the laws about how teachers are hired and fired, specifically the "last in, first out" rules that allegedly protect "grossly ineffective teachers," therefore preventing students, especially minority and low-income students, from getting an equal and quality education. Appeals to the Vergara ruling were filed by California Governor Jerry Brown, California Attorney General Kamala Harris, the California Teachers Association, and the California Federation of Teachers.  On Apr. 14, 2016, the Court of Appeal of the State of California overruled the decision in Vergara v. California. In a unanimous decision, the appeals court ruled that the plaintiffs had failed to show a constitutional violation and as such the court is "without power to strike down the challenged" teacher tenure laws (Vergara v. California - Court of Appeal of the State of California).