What is the purpose of the Shakespearean allusion to Macbeth in Gary Schmidt's The Wednesday Wars?

In January of Gary Schmidt's The Wednesday Wars, Holling is assigned to read Macbeth around the same time Doug Swieteck's brother goes around the schools in town taping clippings of newspaper pictures depicting Holling in his yellow Ariel costume. Doug Sweiteck's brother does this as an act of revenge to regain the power Holling had previously stolen from him earlier in the school year by accidentally tripping him during a soccer game. Holling relates the power-hungry actions of the brother to the power-hungry actions of Macbeth and learns that there is more to life than seeking power.

At the start of the seventh-grade year, Holling joined a football game in which he was up against Doug Swieteck's brother, who was playing forward while Holling was playing defense. Doug Swieteck's brother is the sort of bully who, as Hollin's describes, is heading for the state penitentiary. At first Holling tried to stand his ground, but as he ran away, he says he "left [his] right foot behind," which Doug Swieteck's brother tripped on ("September"). As a result, the brother went hurtling through the air, "like a missile," and crashed his head against the iron goal post, leaving him humiliated for having been taken out by a seventh grader ("September"). By January, the brother is able to get his revenge when Holling is asked to play the part of Ariel in a production of The Tempest. Holling's Ariel costume consists of bright yellow tights decorated with white feathers on the backside. When Holling is featured in the newspaper in his costume, the brother steals every copy of the picture he can get his hands on, enhances all the pictures with bright yellow oil paint, and hangs them everywhere he possibly can for all the world to see. Author Schmidt creates an allusion to Macbeth by having Holling liken Doug Swieteck's brother to Macbeth; just as Macbeth committed murder to gain power, Doug Swieteck's brother did something evil out of revenge in order to regain power. Yet, just as Macbeth falls by the end of Shakespeare's play, Doug Swieteck's brother also falls when Holling gets his own revenge in the form of decking the brother with a very hard and icy snowball.

Schmidt uses the direct reference and allusion to Macbeth to develop a theme concerning power hunger. In discussions about the play with Mrs. Baker, Holling learns that Shakespeare had wanted to teach the following through Macbeth:

That we are made for more than power ... . That we are made for more than our desires. That pride combined with stubbornness can be disaster. ("January")

Through his experiences with Doug Swieteck's brother, Holling sees the truth of those words since he is responsible for the brother's fall from power, twice, despite the brother's attempts to rise in power. Later, Holling is also able to apply the lesson to his power-hungry father by realizing that there is more to life than obsessing over your job.