838 full-time private primary and secondary schools (including kindergartens) in the city, with 258,000 students, accounting for 21.7% of the city's full-time primary and secondary school students. In the compulsory education section, there were 288,000 children of migrant workers who went to schools in Ningbo. Ningbo is one of the top 200 cities in the world by scientific research as tracked by the Nature Index. In the whole year of 2020, the city attracted 1,372 more workers with doctoral degrees, for a total of 9,265; 67,000 highly skilled talents, for a total of 551,000; 35 post-doctoral research stations, for a total of 224; and 166,000 graduates, a year-on-year increase of 20.5%. There are 10 offices, totaling 100. Throughout the year, 327,000 skilled personnel were trained in the city. Higher-Educational institutions Ningbo has 15 universities and colleges as of May 2021, as well as many research institutions that offer graduate degree programs. The following is a list of current universities and colleges in Ningbo. As of 2020, many famous universities and research institutions have an operating campus or institutes in Ningbo, most of them offering graduate degree programs. Compared to the other 14 sub-provincial cities in China, Ningbo has the fewest higher-educational institutions. Secondary and primary education Compulsory education is from the ages 6 to 15. Students are catered to in a variety of state and private schools. Studying for the Gaokao (高考), a cumulative test taken at the end of high school, is optional. At the end of 2020, there were 86 regular high schools with 93,000 students in Ningbo; 35 vocational schools with 69,000 students; 230 junior high schools with 21.7 students; and 427 primary schools with 517,000 students. There were also 838 full-time private primary and secondary schools (including kindergartens) in the city, with 258,000 students, accounting for 21.7% of the city's full-time primary and secondary school students. In the compulsory education section, there were 288,000 children of migrant workers who went to schools in Ningbo. International education Several schools are permitted to operate foreign educational programs as an alternative to the Chinese National curriculum and to accept international students. Access International Academy Ningbo (AIAN) and Ningbo Zhicheng School International (NZSI) both offer the American AERO (American Education Reaches Out) curriculum with the College Board Advanced Placement examinations. Ningbo International School (NBIS) delivers the Cambridge International Primary and Secondary Curricula leading to iGCSE Examinations and A-Levels. Huamao Multicultural