en su clase

in their class

→ en
phrase Rare #34,725
in their class Refers to students in the same school class or group; the possessive can mean his, her, or their depending on context.
SP: María es la más inteligente en su clase.
EN: María is the smartest in her class.

Él es un muchacho aplicado en su clase.

He is a diligent student in his class.

Nancy es la chica más alta en su clase.

Nancy is the tallest girl in her class.

Cuando se trata de matemáticas, él no se queda atrás con nadie en su clase.

When it comes to math, he's not far behind anyone in his class.

A todos en su clase les gusta ella.

Everyone in her class likes her.

Ella es tan lista como cualquiera en su clase.

She is as smart as anyone in her class.

Tom es tan alto como cualquier niño en su clase.

Tom is as tall as any other child in his class.

Nadie más en su clase puede correr tan rápido como él.

No one else in his class can run as fast as him.