If anything "don't know" could be in the middle:

 1. Agree Strongly 
 2. Agree
 3. Don't Know
 4. Disagree
 5. Disagree Strongly

[Here's][1] a similar Likert scale discussion.

Also, as @PeterFlom noted, you have more "agree" answers than disagree. Likert himself [recommended](http://www.voteview.com/Likert_1932.pdf) using equal number of right and left answers. The paper is rather fascinating, btw, I suggest reading it in full.


  [1]: http://www.simplypsychology.org/likert-scale.html