Character Analysis
Sylvia and Phyllis are two of Rachel's classmates, and Rachel doesn't have many nice things to say about them. She thinks Syliva is "stupid" and that the girl doesn't like her "maybe because [she's] skinny" (9). She considers Phyllis "even dumber than Sylvia Saldívar" (20).
With that said, we must remember that Rachel is going through an emotionally trying eleventh birthday, and these two peers, whether accidentally or not, have had a hand in the entire fiasco. It's entirely possible that these descriptions are Rachel's way of lashing out, of internally trying to hurt these two for the roles they played in her embarrassing day. Rachel could be an unreliable narrator or not, depending on how you read the story. Either way, we think Sylvia and Phyllis sound like pretty uninspiring classmates too. Don't worry, Rachel, we've got your back.
Yackety-Yak, Don't Talk Back
One thing we can say for certain about these two girls: They serve as foils for Rachel. A foil is a character that contrasts the qualities of another character—usually the protagonist—to heighten our understanding of both.
In this case, Sylvia and Phyllis have one thing Rachel does not: a voice. Sylvia tells Mrs. Price she thinks the sweater is Rachel's, and those words have the power to set off the entire awful day. Phyllis finally admits the sweater belongs to her and that puts an end to it, even though the emotional damage has been done.
In both cases, the power of voice allows these two girls to sway Mrs. Price and the situation in ways Rachel cannot. Unlike these two, Rachel finds that when she "open[s] [her] mouth nothing comes out" (9).
A voice grants power and agency for the girls in Mrs. Price's classroom, as evident by Sylvia and Phyllis. (It works for Mrs. Price, too). Unfortunately for Rachel, who has some amazing things to say internally, a voice is something she lacks.