[racket] Separate files in the HtDP languages?

On their next assignment, my students will reuse code they have
built for binary search trees.  I would prefer that they place the
old code in a different source file than the new code.  I tried
doing this using "require", but I cannot figure out how to get
"require" to load a file that is written in Intermediate Student Language.
Is there another mechanism I should try?  Is the thing I want to do
even possible?


Norman