Original: They are forced to sit in a chair for a certain amount of time and to quietly complete assignments.
My opinion: They are forced to sit in a chair for an exact amount of time and forced to sit quietly and finish assignments not knowing if they have to stay there after the bell rings.
The author is trying to say that it's worthless to be classified as a citizen if you cannot vote, just as it is worthless to have a boat if you have no oars.
