Catholic schools are the largest non-public school system in the United States. In 2010, 2 million students attended 6,980 schools. 331 of these are private. Catholicism of schools in the United States was first established during the 19th century with the arrival of English immigrants. Catholic schools in the USA are significant in that Catholicism is seen to have been critical in developing the American culture. The development and enrollment of Americans into Catholic schools increased after World War II, Post-war development and Cold War in the battle against anti-religious Communism. By the time of 1964–1965, Catholic schools accounted for nearly 89% of all private school attendance and 12% of all school-age children in school (K-12) in the USA. The number of religious (priests, brothers, and sisters) was at its highest, allowing schools to offer qualified teachers at minimal costs, meaning that most children in the 1940s and 1950s attended their parish school free of charge. Since then, despite American Catholics' widely favorable views of these institutions, there has been a large decline in enrollment predominantly believed to be due to "“suburbanization, liberalization of education and the rise of the Catholic middle-class.”" In the United States, Catholic schools are accredited by independent and/or state agencies, and teachers are generally certified. Schools are supported through tuition payments, donations, and fund raising charities.