Note: Recently, the "missing context" close reason was given a link which, in my opinion, makes it fair to both remove the "homework" close reason and close "copy/paste" questions.
The rest of this answer is now outdated.
How should the "lack of context" and "homework" reasons be used?
I like zyx' idea to remove the "homework" reason, but I believe a bit more should be done.
Let me give a short intro on my thoughts on the subject. I often find close reason "Off-topic" on questions where the OP made no effort. And, however I agree on closing these, there is nothing in the help system on that. The "On-topic" page of the help system has an extra explanation on homework questions, which says:
Also, please put some work into formulating your question. Please do not just copy and paste the exact question text from your homework sheet.
But, for general questions, there is no "show an effort" request. So, when we close a question for being "off-topic", the OP gets the link to what is on-topic, and there is nothing there to explain to him that his effort is what is missing. In my opinion, this is wrong, and - for this reason - I vote "Leave open" on effortless questions (unless there is some other problem with them).
So, why is this "show effort" request there only for homework questions? Do we want people to try to fake that their homework is not a homework, but a "regular" question? Why the (imaginary) difference between the to?
In my opinion, this should be a general guidance: we want to help, not solve your problems for you.
To summarize my suggestion:
Add "we want to see some effort on your side" as a general guidance on all questions. Basically, homework questions guidance should be adapted and made into a "guidance for all questions". A short "show effort", with link to that guidance, should be put in the "On-topic" page of the help system.
Remove the "homework" reason, because -- given that we do what I suggest in the point 1 -- homework questions stop being "special".
Add close reason for "no effort".
"No context" reason should still be there, although I don't expect it to be used often (if the above is accepted).
The actual texts should, of course, be written more nicely. I can edit them if there is a general interest to go in this direction; especially if some good ones are suggested in the comments.