Any difference between 发蒙 and 上学 for children? Sometimes the words 发蒙 and 上学 can be seen together as a single phrase: 发蒙上学.

Working with the topolectical words 穿牛鼻子

one defintion says:


  喻指小孩到学校读书


while another says:


  比喻儿童发蒙


Is there any, fundamental, difference between 发蒙 and 上学 for children?

Or is this just more of a countryside (乡下) vs. urban idea?

This ifeng article says:


  自古以来，孩子上学叫“发蒙”，早期教育叫“蒙学”。从文字角度，“蒙”这个字最早的含义，本身就与幼童启蒙有关。


It's not super clear if it is exactly the same or if there are subtle differences.
发蒙 is not used constantly in Chinese anymore. 

上学 means receive education in a general way.

if you want to say education at an early age, maybe "启蒙教育" fits better.