Report card far from accurate
To say that Linux and open source applications deserve an "A" in every category is really far too generous. An "A" on a report card typically means that it goes "above and beyond" the minimal requirements for an assignment. This might imply that there is little room for improvement. On the contrary, I believe that Linux educational applications are just barely adequate.
To my knowledge, there are only three gradebook applications in active development: OpenGrade, Iona Student Online, and Grades XML editor; none of these approach the easy-of-use or features available in commercial applications. (No gradebook software can be considered mature or finished at this point, IMO.)
I would give each education-related category a C+ or B-. The Linux desktop is a B+, about the same rating I'd give to Windows and Mac OS Classic. The server software, where Linux shines, is fairly mature so I'd give it an A-.
Giving it such a relatively low grade is not really a problem; it just shows that Open Source educational/administrative programs have a ways to go. It's also questionable whether any product is truely perfect and deserves the prestigious "A+". Unlike the meritocracy of high school education where a bad grade can blemish one's future, being able to say "this needs improvement" can be beneficial.
Disclaimer: IANAT (I am not a teacher)