[RonF]

The "teacher" is unaware, here, that the "work" could be done using a program other than "explorer".

Not necessarily. I could have said this myself in the sense of "Close Firefox and finish your work using Explorer."

This kid needs to stop being a wiseass trying to show someone how slick he is and follow the rules.

[ArrogantBustard]

The way I read the note, the kid was instructed to do "the work" (whatever that may have been).

He apparently was doing the work.

The teacher needs more thorough "subject matter knowledge".