The Stanford Achievement Test Series, the most recent version of which is usually referred to simply as the "Stanford 10" or SAT-10, is a set of standardized achievement tests used by school districts in the United States and in American schools abroad for assessing children from kindergarten through high school. Millions of students have taken the test each year. First published in 1922, the test is now in its tenth version. It is produced by the publishing company Harcourt, and should not be confused with the SAT college admission test published by the College Board. Although in many states it is being replaced by state-created tests, it is not equivalent to most of these tests in that the Stanford series are more comprehensive in scope than the newer assessments. The test is available in 13 levels that roughly correspond to the year in school, but the correspondence is not exact. Each level of the test is broken into subtests or strands covering various subjects such as reading comprehension, mathematics problem-solving, language, spelling, listening comprehension, science, and social science.