Why did Ji-li's parents hide the information about them having land lords?
I think that her parents did not want to create another impact for Ji-li since she has had more impacts in the past. The wall picture tells me that you can't jump over it unless you have gear. The parents are basically now allowing her to know about the information they are hiding until she's ready.
Ji-Li wanted to become a educable child, but why did she plan to break with her family?
I simply believe the reason why she broke apart was because of the newspaper article. It told that Ji-li's family was rich. She blames it on her grandfather and if it was me, I couldn't have studied and have a normal life with all that chaos happening around her family.
Why did Ji-Li run away from school?
She was.. ashamed. She went to school to help the revolutionary committee but she saw that she was "replaced" because of her political status. She runs away and realizes that her black family is getting worse.