GUANGZHOU, May 25 (Xinhua) -- China's Ministry of Education said Friday that the country has examined 128,418 after-school training institutions, among which 12,251 have had their issues rectified as of Wednesday.

At the beginning of this year, China launched a campaign targeting after-school institutions for potential safety loopholes and unlicensed operation, Lv Yugang, an elementary education official at the ministry, said at a conference in south China's Guangzhou.

The campaign also targeted after-school training institutions which place students under too much pressure.

A total of 217 teachers or principals at 139 schools across the country were punished for substandard teaching in class while teaching in after-school programs for profit.

A report from the Chinese Society of Education estimated that after-school programs received more than 137 million students in 2016.