Can you change a selection of dropdown list to affect another?

Can you change a selection of dropdown list to affect another?

I am creating a School List, and when i select a certain school i want a second drop to give me the name of the classrooms at that school.

For Example:
i choose Diamond Elementary i want the second drop down to give me AM and PM selection
but if i choose Lincoln i want it to give me the selection of 12AM, 12PM and 15AM, 15PM

is that possible?