Academic education simply refers to private schools, including private kindergartens, private primary schools, private secondary schools and private universities. As long as the education authorities allow enrollment, it is legal and the academic qualifications are recognized by the state. Private universities are also admitted through the general college entrance examination. Some private universities also enroll adult higher education and pass the adult college entrance examination. The forms of study are correspondence and amateur.
The state runs public schools, while private investment runs private schools. Correspondence is a learning form of adult higher education, which is accepted by adult college entrance examination.
So, when you talk about correspondence VS joint exam, one is the learning form of adult education, and the other is the correspondence joint exam.