en su clase

in his/her class

→ en
phrase Rare #43,372
in his/her class Su can mean his, her, their, or your (formal), depending on context.
SP: Hay veinte estudiantes en su clase.
EN: There are twenty students in his class.

Ella es tan lista como cualquiera en su clase.

She is as smart as anyone 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.

Tom es tan alto como cualquier niño en su clase.

Tom is as tall as any other child in his 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.