A jerk is a mean or unkind person. He is probably referring to a classmate who would be mean to him when the "jerk" sees the wimpy kid's book.
[I look forward to improving my Spanish so one day I can read books in Spanish]
So great that you are reading those books. In that particular sentence, the word "jerk" refers to a contemptibly foolish person, in other words, a person that is an idiot or moron, usually with no nice intentions.
In other cases, the word "jerk" can mean a quick, sharp, sudden movement (noun).
But to use the word "jerk" as a verb would mean to move or cause to move with a jerk. "the van jerked forward"
Also, as an interesting fact, jerk is a style of cooking native to Jamaica, in which meat is dry-rubbed or wet marinated with a hot spice mixture called Jamaican jerk spice. Some historians believe it was originally developed by African slaves who escaped into the wilds of Jamaica when the British captured the island from Spain in 1655.
Hope this helps.