LitCharts assigns a color and icon to each theme in Wonder, which you can use to track the themes throughout the work.
The Difficulty of Kindness
Independence and Growing Up
Status and Bullying
Identity
Parenting and Guidance
Summary
Analysis
A few minutes later, Via returns with a boy named Justin. He wears round glasses, carries a long case with a sharp end, and seems nervous. August mischievously asks if Justin is Via's boyfriend, and Jack asks if there's a gun in his case. Justin nervously explains that he plays the fiddle in a zydeco band. August suggests that Justin tell people that he has a gun so people wouldn't mess with him. Justin tries to explain that zydeco is a kind of music from Louisiana, but Jack struggles to not laugh when Justin says he's from Brooklyn, not Louisiana. Via pulls Justin out, closes the door, and August and Jack start laughing hysterically.
Though the age difference between Justin and August complicates things somewhat, Jack and August's teasing shows them engaging in a power play over someone who has relatively less power (he is romantically involved with Via and this is his first time visiting the house, meaning he probably feels very vulnerable). This shows that even as nice as Jack and August are most of the time, they're not above this low-grade teasing when it suits them.