They arrive at school at a quarter to eight.
Here's a breakdown:
* Llegan: This is the third-person plural present tense of "llegar," meaning "to arrive."
* a la escuela: This means "to the school."
* eso de: This is a phrase that indicates an approximate time.
* las ocho: This means "eight o'clock."
* menos cuarto: This means "a quarter to" (i.e., 15 minutes before).