Currently you are able to search by grade level and school zone when enabling schools in the filters tab.
Here are instructions on how to do so:
1. Log in to your Zillow app
2. Type in the location desired into the address bar
3. Go to "Filter" >> Switch 'Schools' to ON >> choose your criteria
From here, you can click on the school of your preference and you will have the option to select "View homes assigned to this school."