Help me understand/translate "不留到晚自习就写完多好" (context supplied) I'm struggling to understand this sentence. It's in an answere here, about halfway down the page. I've copied the context below:


  一部分是课代表。我是语文课代表 也很喜欢语文老师 他忘了留作业的话 我就在座位用口型告诉他 作业。然后他就
  噢今天的作业啊，巴拉巴拉。这样可以避免我去办公室问作业 作业总是要有的啊。 一部分单纯热心。而且想提前写作业 不留到晚自习就写完多好。
  最少的一部分是自己从来不写作业 但不能让别人没有作业。这种可能很小。


Anyone able to help me out with this? I'm HSK5 so I know the general meaning of the characters in the sentence but I can't figure out the overall meaning. Thanks in advance.
Because there is some uncommon term that OP don't understand. 

课代表 so call "class/course representative", is in fact, a helper/assistant roles appointed by the tutor/teacher.  So the author is a "helper" . 

这样可以避免我去办公室问作业  : So as a helper, he/she may need to go to the teahcer office to ask about home work for the student if the teacher forget about it.

而且想提前写作业 不留到晚自习就写完多好. What the author mean the he/she are able to do the home work immediately during those spare time between the class, rather than leaving it overnight.