See the compatibility table near the bottom of this page:
Start Edition files can only be opened with a full/commercial version (or Start itself of course).
Once saved by the commercial version, it appears that EDU can open the resulting file. (It does seem odd that EDU cannot open a Start file directly - hard to see the marketing reasons for preventing it.)
A more detailed table of which versions of Start files can be opened in which versions of (commercial) AC is here: