The education system in the United States is unique in comparison to other higher education systems around the world as it operates with a high level of decentralization and independence from federal government regulation. The US education system is divided into primary school, middle school, secondary school, and postsecondary education. There are several types of higher education institutions in the US, including public and private universities, technical institutes, Ivy League schools, liberal arts colleges, and community colleges. Higher education in the US includes non-degree programs leading to certificates and diplomas, as well as six degree levels ranging from associate to research doctorate. The US education system is widely recognized for its flexibility and allows students to specialize in their chosen field of study. Unlike centralized education systems, each institute in the US determines its own programs and admission standards. Although the US education system does not offer a second or higher doctorate, it does provide postdoctoral research programs.