 "Newsweek" again ranked Clayton in 2012; its ranking was 129 of the top 1,000 schools.When Clayton sophomores participated in the Programme for International Student Assessment (PISA) in 2009, the school's average scores in science and reading were higher than the averages of all other participating countries, including the United States; its average score was second-highest as compared to participating countries in mathematics.Clayton has a relatively low dropout rate and a high graduation rate; for the 2010–2011 school year, fewer than 1 percent of students dropped out compared to the Missouri state dropout rate of 3.4 percent.