"Why are they expanding the school?"
Translation:Warum erweitern sie die Schule?
Hm... not sure. I think the main meaning of ausbauen here would be something like "complete", as in to make portions which were previously not usable (perhaps because the budget had not been enough to complete that wing and so it was just a concrete shell), usable (perhaps by putting in internal walls, wallpapering, etc.).
Rather than adding a new wing.
Why not wofür? It seems more appropriate here, "what for", for what purpose