George W. Bush signs the No Child Left Behind Act on Jan. 8, 2002, surrounded by school children and supporters of the bill, including Senators Edward M. Kennedy (D-MA) and John Boehner (R-OH). Source: "George W. Bush: Moments That Defined His Presidency," www.washingtonpost.com/AFP (accessed June 16, 2011)
Standardized tests have been a part of American education since the mid-1800s. Their use skyrocketed after 2002's No Child Left Behind Act (NCLB) mandated annual testing in all 50 states. US students slipped from being ranked 18th in the world in math in 2000 to 40th in 2015, and from 14th to 25th in science and from 15th to 24th in reading.  Failures in the education system have been blamed on rising poverty levels, teacher quality, tenure policies, and, increasingly, on the pervasive use of standardized tests.
Proponents argue that standardized tests are a fair and objective measure of student ability, that they ensure teachers and schools are accountable to taxpayers, and that the most relevant constituents – parents and students – approve of testing.
Opponents say the tests are neither fair nor objective, that their use promotes a narrow curriculum and drill-like "teaching to the test," and that excessive testing undermines America's ability to produce innovators and critical thinkers.
Standardized tests are defined by W. James Popham, former president of the American Educational Research Association, as "any test that's administered, scored, and interpreted in a standard, predetermined manner."  The tests often have multiple-choice questions that can be quickly graded by automated test scoring machines. Some tests also incorporate open-ended questions that require human grading, which is more expensive,  though computer software is being developed to grade written work also. 
Many kinds of standardized tests are in use, but high-stakes achievement tests have provoked the most controversy.  These assessments carry important consequences for students, teachers and schools: low scores can prevent a student from progressing to the next grade level or lead to teacher firings and school closures,  while high scores ensure continued federal and local funding and are used to reward teachers and administrators with bonus payments. 
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Chart comparing mathematics performance of students in 65 countries/economies on the 2009 Programme for International Student Assessment (PISA) Source: Organisation for Economic Co-operation and Development (OECD), PISA 2009 at a Glance, www.oecd.org, 2010
Standardized testing in the US has been estimated to be "a multi-billion-dollar industry," though proponents have accused opponents of exaggerating its size.  The largest test publishers include NCS Pearson, CTB/McGraw-Hill, Riverside Publishing, and Educational Testing Service (ETS). 
The earliest known standardized tests were administered to government job applicants in 7th Century Imperial China.  The tests, built upon a rigid "eight-legged essay" format, tested the applicants' rote-learned knowledge of Confucian philosophy and were in widespread use until 1898.  In the Western world, the Industrial Revolution ushered in a movement to return school-age farmhands and factory workers to the classroom. Standardized examinations enabled the newly expanded student body to be tested efficiently. 
In the mid-1800s, Boston school reformers Horace Mann and Samuel Gridley Howe, modeling their efforts on the centralized Prussian school system, introduced standardized testing to Boston schools. The new tests were devised to provide a "single standard by which to judge and compare the output of each school" and to gather objective information about teaching quality. Boston's program was soon adopted by school systems nationwide.  Concerns about excessive testing were voiced as early as 1906, when the New York State Department of Education advised the state legislature that "it is a very great and more serious evil to sacrifice systematic instruction and a comprehensive view of the subject for the scrappy and unrelated knowledge gained by students who are persistently drilled in the mere answering of questions issued by the Education Department or other governing bodies." 
The Kansas Silent Reading Test (1914-1915) is the earliest known published multiple-choice test, developed by Frederick J. Kelly, a Kansas school director. Kelly created the test to reduce "time and effort" in administration and scoring. 
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Archival photo of the IBM 805 test scoring machine, used to grade standardized tests from the 1930s-1960s. Source: IBM Archives, "IBM 805 Test Scoring Machine," www.ibm.com (accessed June 16, 2011)
In 1934, International Business Machines Corporation (IBM) hired a teacher and inventor named Reynold B. Johnson (best known for creating the world's first commercial computer disk drive) to create a production model of his prototype test scoring machine. The IBM 805, announced in 1938 and marketed until 1963, graded answer sheets by detecting the electrical current flowing through graphite pencil marks.  The contemporary use of No. 2 pencils for exams is a historical holdover, since modern scanners' optical mark recognition (OMR) technology can recognize marks made by pens and pencils alike. 
Modern Testing Begins
The modern testing movement began with the Elementary and Secondary Education Act (ESEA), enacted by President Lyndon Johnson in 1965, which included testing and accountability provisions in an effort to raise standards and make education more equitable. 
The 1983 release of A Nation at Risk: The Imperative for Educational Reform, a report by President Ronald Reagan’s National Commission on Excellence in Education, warned of a crisis in American education and an urgent need to raise academic standards.  The report's portrayal of an education system that had "lost sight of the basic purposes of schooling, and of the high expectations and disciplined effort needed to attain them" rallied reform advocates to press for stricter accountability measures, including increased testing. 
Successive administrations attempted to implement national school reform following A Nation at Risk's release. George H.W. Bush's America 2000 plan aimed to achieve world's best math and science test scores by the turn of the century, but became mired in Congress. Bill Clinton's Goals 2000 Act and Improving America’s Schools Act (IASA), both passed in 1994, instituted a voluntary system of testing and accountability, but few states complied. Clinton's 1997 Voluntary National Test initiative languished in Congress and was abandoned after $15 million and over two years had been spent on its development. 
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Denver Post cartoon satirizing the effect of standardized tests on public education. Source: Mike Keefe, Denver Post, 2002
No Child Left Behind and Race to the Top
The No Child Left Behind Act (NCLB) passed with bipartisan support (381-41 in the House of Representatives and 87-10 in the Senate) and was signed into law by President George W. Bush on Jan. 8, 2002.  The legislation, modeled on Bush's education policy as Governor of Texas, mandated annual testing in reading and math (and later science) in Grades 3 through 8 and again in 10th Grade.  If schools did not show sufficient "Adequate Yearly Progress" (AYP), they faced sanctions and the possibility of being taken over by the state or closed.  NCLB required that 100% of US students be "proficient" on state reading and math tests by 2014, which was regarded as an impossible target by many testing opponents.  According to the Pew Center on the States, annual state spending on standardized tests rose from $423 million before NCLB to almost $1.1 billion in 2008 (a 160% increase compared to a 19.22% increase in inflation over the same period).  Combined state and federal government spending on education totals $600 billion per year, while all-time philanthropic contributions to US education total less than $10 billion, according to a 2011 statement by education philanthropist Bill Gates. 
On February 17, 2009, President Barack Obama's Race to the Top program was signed into law, inviting states to compete for $4.35 billion in extra funding based on the strength of their student test scores. On Mar. 13, 2010, Obama proposed an overhaul of NCLB, promising further incentives to states if they develop improved assessments tied more closely to state standards, and emphasizing other indicators like pupil attendance, graduation rates and learning climate in addition to test scores.  Testing opponents have decried both initiatives for their continued reliance on test scores, a complaint Obama seemed to echo on Mar. 28, 2011, when he said: "Too often what we have been doing is using these tests to punish students or to, in some cases, punish schools." 
The 2010 documentary Waiting for Superman gave the testing and accountability movement a nationally recognized spokesperson in Michelle Rhee, then-Chancellor of Washington, DC, public schools. Rhee, appointed by DC Mayor Adrian Fenty in June 2007, became a lightning rod for testing opponents after she enacted a strict policy of teacher and school accountability based on standardized test scores. By the time she resigned her post in Oct. 2010, she had fired 600 teachers and dozens of principals, closed 23 schools,  and introduced $25,000 bonuses to teachers receiving high evaluations, based in part on standardized test results.  DC's student test scores rose under Rhee's reforms, but in Mar. 2011, a USA Today report uncovered scoring irregularities (high numbers of answers that had been erased and replaced with correct answers) in 103 DC public schools during the 2008-2010 school years.  Rhee responded by saying "the possible misguided actions of a few individuals do not cloud the incredible achievements of the majority of hard working educators who serve our children," and touted nation-leading gains by DC students
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Newsweek's Dec. 13, 2010, cover featuring standardized test proponent Michelle Rhee, former Chancellor of Washington, DC, public schools. Source: "Thought-Provoking Lineup of Next Philadelphia Speakers Series to Start with Education Leader," www.widenermagazine.edu, Mar. 31, 2011
on the National Assessment of Educational Progress (NAEP).  Despite claims by DC public school officials that the anomalies were in fact limited to one school, a confidential Jan. 2009 memo uncovered in Apr. 2013 revealed that the problems may have been more widespread. The memo, prepared by an outside analyst hired by Rhee, noted that 191 teachers in 70 schools were "implicated in possible testing infractions." Nearly all the teachers at one DC elementary school "had students whose test papers showed high numbers of wrong-to-right erasures," according to USA Today.  However, on Jan. 7, 2013 the US Department of Education’s Office of Inspector General said an investigation had found no evidence of widespread cheating on the DC Comprehensive Assessment System tests from 2008-2010.  The cheating scandal continued after Rhee left her position. The Washington Post reported in Apr. 2013 that 18 DC public school teachers were found to have committed "'critical' violations of test security" in 2012.
In Aug. 2010, the Los Angeles Times spurred a national controversy when it announced plans to publish the names of 6,000 Los Angeles elementary school teachers, alongside calculations of their students' gains and losses on standardized tests during the school year. Known as the "value added" method of evaluating teacher effectiveness, it has been mandated by several hundred school districts in 21 states.  Up to 40% of New York teachers' evaluations are tied to value-added test score analyses, as of the 2011-2012 school year. 
On March 9, 2011, US Education Secretary Arne Duncan told Congress that 82% of American schools could fail to meet NCLB's goal of 100% proficiency on standardized tests by 2014. Duncan proposed reforming NCLB to "impose a much tighter definition of success" that supports "our fundamental aspiration that every single student can learn, achieve and succeed."  Individual states have cast similar doubts on their ability to satisfy NCLB's Adequate Yearly Progress goals. A 2008 study published in the peer-reviewed journal Science forecast "nearly 100 percent failure" of California schools to meet AYP in 2014.  The primary reason for failure, the study concluded, would be poor results on standardized tests by English Language Learners and children in low-income families.