Depends on how serious your school is.. in my detention we kind of just goofed off, ignoring the work given to us to do, but they didnt care.
here in uk, after school detention you have to do work or read, as long as you are silent and don't make any noise, if you do then your time gets extended in detention.
How would we know .. ask someone in your school that had detention.
i just ditch. its how i roll