BEIJING, July 17 -- China aims to eliminate "super-sized" classes that accommodate more than 66 students in primary and middle schools nationwide by the end of 2020, according to a guideline released Wednesday.

The proportion of "large-sized" classes with over 56 students will be kept to no more than 5 percent by 2020, said the document, jointly issued by the Ministry of Education, the National Development and Reform Commission and the Ministry of Finance.

Oversized classes have long been a prominent issue in China's compulsory education system, as quality education resources are insufficient in some regions.