I was hoping to be able to do the same thing, but the only way I was able to do that (on the app anyway) was to compare a school district map with the Trulia map, and use the 'draw' icon to draw a line around the school district borders. Once you've drawn the outline, you can click save search and name it. In your settings you can then choose to be alerted when new homes go on the market within that school district. Hope that helps! If anyone knows a quicker way to do it, please share!