Updated Saturday at 1:08 p.m. ET.
On Friday, Los Angeles teacher Rosa Jimenez started her U.S. History class with a question for her students:
"What does a labor union do?"
The juniors inside the library at Robert F. Kennedy Community Schools flip through their notes. From the back of the room, a student named Ingrid shoots up her hand:
"A labor union is an organization of workers that's formed for the purpose of benefiting the workers," she explains. They deal with "wages and benefits and working conditions."