I wonder if the following strings may be confusing to English speakers:
$string['configfixedstudents'] = 'Fixes the students column in the grader report, allowing the grades to scroll horizontally.';
$string['fixedstudents'] = 'Fixed students column';
I think someone may read 'Fixed students column' and think that this one is fixing something that was broken rather than providing a static student column. I would probably stick with the singular hear because you are referring to a single column called students, so perhaps 'Static student column' might be better. The same is true of the config description. I think we are trying to say that it: "Allows grades to scroll horizontally by adding a static student column".
Peace - Anthony