In Social Explorer, click on the link for "Maps" in the upper right, then under US Demography, click on Start Now. Once you're at the map, you can either zoom in on the area of interest, or search for an address. When you've zoomed in, you will see the map divided into census tracts; these are geographic units created by the Census Bureau, each of which contains about 4,000 residents.
To create a report, click on the hamburger menu in the upper right and select Create Report. Now you can change the geographic unit by clicking on the drop-down menu where it says Census Tract--UNSD signifies unified school district. Click on the area you want a report on, then select the topic for your report, then click on Create Report.
In Social Explorer, click on the link for "Maps" in the upper right, then under US Demography, click on Start Now. Zoom in on the area of interest. Click on the Change Data button in the upper left to select the year and variable to map. Under "Show data by," expand the menu and turn off the Automatic button, then select the geographic unit you want. You can change the way the data are visualized under "Visualization type." Click on Export in the upper right to create an image file of your map.
In ELSI, click on "Begin" in the expressTables button. You'll see that you have a few boxes where you can make selections.
Select a Level: Choose Public School.
Select a Table: These are the kinds of information you can retrieve about a school. Most of the interesting options are under Enrollments, where you have demographic information about the student.
Next you can select the schools you want--for example, by district or county. Then click Vew Table.
The API is just a URL, starting with http://api.census.gov/data/, with components that tell the Census Bureau server which data you want. For example:
?get=NAME,B01001_001E variables that you want
&for=school+district+(unified):* geographies that you want
&in=state:23 area within which you want
All of these components can be replaced with others to get different data.