Generally it is 1:30, but conditions are different in every place.

Producers and operators of ordinary meals for students, nutritious meals for students, and recess meals for students should obtain a catering service license from the food and drug supervision and management department at or above the county level where they are located. Student nutrition meal production and operation of the food service license must be permitted to "student nutrition meal" licensing program. Not receive a food service license shall not produce and operate student meals, student nutrition and student meals.