If req fields aren't filled there is an error message nearby the fields. But the screen shown for the teacher is on bottom of the page and most of the time he didn't see the error informations because they are on top of the page. .
The problem is also on updated systems where fields that are required in 1.8 (but not in 1.7) are empty. If I make changes in the setting pages after saving the changes the pages is shown at the bottom, but I don't see informations about the missing entries in req fields.