Get your teachers to mark your answers; even if they don't want to, they can't say 'no'. Otherwise, scan your answer and email it to a friend to mark. But don't mark it yourself, even if you have the marking guidelines because there is no way that you cannot be subjective. Alternatively, just go through your responses and write notes on what you could have done better; I do that and (when in exams) I pay more attention to those aspects of my responses as thery don't come as naturally to me.