If your ancestors were educated in German universities, they may have been recorded in the matriculation records of their schools. The library has a limited number of these records for the sixteenth to the twentieth centuries. They are not available for all states.
School records sometimes contain valuable information, such as your ancestor's name, age, hometown, and enrollment and graduation dates. Sometimes they contain biographical information, including names of parents, wife, and children. The few school records that the Family History Library has are listed in the Place Search of the Family History Library Catalog under:
GERMANY - SCHOOLS
GERMANY, [STATE] - SCHOOLS
GERMANY, [STATE], [UNIVERSITY TOWN]
The university may have kept original school records (and any published versions). In some areas, local or state archives may have these records. You can find citations for German university matriculation sources on pages 181 to 197 of Ribbe's Taschenbuch für Familiengeschichts forschung.
Though you may not be successful in getting the information you want, you can try writing for school records. Address your letter to the town and school in which you are interested. The Family History Library does not have the addresses of German schools.