It's a casual way to ask about what's happening at someone's school. It's similar to asking "What's new?" or "How's it going?" in English.
Here are some possible responses:
* "Nada nuevo": Nothing new.
* "Un montón de trabajo": Lots of work.
* "Tenemos un examen": We have an exam.
* "Un evento deportivo": A sporting event.
The answer will depend on the specific situation and what's happening at the school.