I have to proctor from Monday to Friday.
All the teachers of this school were assigned/asked to proctor during the period of the mid-term exam(ination) without any exception.
2006-04-20 12:21:03 補充：
Thank you for backing me up,Jason.
But, indeed, "during" has the meaning of "within a certain period of time".
At frist, I was an English speaker, then I went back to a Chinese by making mistake like that.
By the way, using proctor is still more explicit.
2006-04-24 16:08:18 補充：
Ha Ha! Nice to "see" you again. Frost.
2006-04-24 18:40:35 補充：
To my knowledge, you could use either "midterm" or "mid-term exam".
But if your are talking to a foreigner instead of a native of the states, "mid-term exam" may be more vivid.