Here's a breakdown:
* En la escuela: "In the school"
* los alumnos: "the students"
This phrase is commonly used to describe something related to students within a school environment.
For example:
* En la escuela los alumnos estudian matemáticas. (In the school the students study mathematics.)
* En la escuela los alumnos comen en el comedor. (In the school the students eat in the cafeteria.)